web terms and error codes

Common web terms and error codes -latest update: 2007-01-30

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     fyrskeppsvagen.com

Definition List of Web Terms       Error codes
| a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x |
Address	either the address of a user of a system, as in an email address (required so that the message sent can be directed to the desired person), or the address of a site on the internet
Anonymous FTP	this enables a user to retrieve files from another site on the internet without having to establish a user-ID and password on the system.
ANSI	american national standards institute - ANSI is responsible for approving standards in many areas of the net
Apache	a public domain web server developed by a group of programmers. The first version of Apache was developed in 1995. Because it was developed from existing NCSA code plus various patches, it was called a patchy server, hence the name Apache Server. As a result of it's sophisticated features, excellent performance, and low price (it's free), Apache has become the world's most popular web server. By some estimates it is used to host more than 50% of all web sites in the world
Applet	an applet is a java program designed to run in a web browser and implement features on a web site
Archie	a system for finding publicly available files for FTP over the Internet
Backbone Net connection	a backbone is a set of paths that local or regional networks connect to for long distance communication. The connection points are known as network nodes or telecommunication data switching exchanges (DSE's)
Bandwidth	the maximum amount of information passed over a connection in one second. It is measured either in Kbps ( kilobits per second ) or Mbps ( megabits per second)
Baud	this is the speed of a modem, written as the number of transitions in modem signals per second. Each transition can carry more than one bit of information
Bits	denote units of data. One byte consists of eight bits ( each either a 1 or a 0 ). Bits are the measurement used for data transmission speeds, as in a 56 kilobit modem. Bytes are used when talking about memory and disk space as in megabytes and gigabytes
Blinking	using an offline reader to access on online system
Bounce	this is when email is returned undelivered
BPS	bits per second - this is the speed at which bits are transmitted
BSD	is a popular and free version of UNIX that runs on Intel microprocessors. Free BSD is distributed in executable and source code form. The source code enables ambitious users to actually extend the operating system
Cache	this is a temporary storage space where your browser stores the files it downloads from the web. Web pages are stored in cache to speed up your web browsing
CGI	common gateway interface - a standard way for web servers to pass control to an application program and then receive data back when it's done. It enables application programs to run on your behalf as part of your web connection on any kind of operating system (OS)
Chatroom	a place online where you can exchange text messages in real-time with a group of like minded people
Click through	a page hit established by a viewer choosing a visible link (usually referring to a banner advert)
Client	an application such as a web browser or newsreader that extracts information from a server on your behalf. Also taken to mean any piece of software that accesses information via a network
Connect time	the length of time you spend online to the net
Cookie	some web sites place a cookie on your computer when you visit them. So if you return to the site, it will be able to read the cookie to see what you did on your last visit and add more information
CPS	characters per second - a measurement of data output speed
Data compression	the compression of information to decrease transferred file size. MNP5 and V.42bis are the best known types
Decryption	decoding encrypted data to it's original form
Dial up	to connect to another computer by calling it over the telephone network
Digital Certificate	in the common security standard for online transactions called SET, a digital certificate is issued by banks ( for example, a Mastercard or Visa issuer) to each patron and each merchant to identify them as a valid transactor
DNS	domain name system - enables domain names to be resolved into numerical addresses (IP-address) Eg. fyrskeppsvagen.com -> 81.226.31.75
Dynamic pages	dynamic HTML is a collective term for a combination of new HTML tags and options, style sheets and programming, which enable you to create web pages that are more interactive and faster to download
E-business	the term coined by IBM to describe it's e-commerce solutions, now commonly in use as a generic term
E-commerce	the process of buying and selling over the Internet
Encryption	a method of coding data to prevent unauthorised access, most commonly used on the net to protect email
Ethernet	a method for connecting computers to a network using coaxial cable
E-wallet	when using e-cash, Wallet software enables several methods of payment to be defined within the wallet (several different credit cards) and puts all your verification in one area
Extranet	A secure link via the internet joining different companies intranets.Encryption, password protection and firewalls provide added security. The concept behind the extranet is that html based information and data stored in a companies database can be shared securely between companies on the extranet.
FAQ	frequently asked questions - to be found all over the Internet - in Usenet newsgroups , mailing lists, as FTP, Gopher and WWW sites
File server	a computer that stores files on the Internet making them available for access by various net tools
File size	number of bytes of memory making up a file. Most search engines limit banner sizes to between 8k and 15k
Firewall	a security device to help protect a private network from Internet hackers. It is a machine with two network interfaces, configured to restrict which protocols can be used across the boundaries, and to decide what internal IP addresses can be seen to the external Internet
Forum	a message area on CompuServe or Delphi, equivalent to an echo of FidoNet, a newsgroup on Usenet or a conference on CIX
foo	Metasyntatic variable. A metasyntatic variable is a string that stands for or represents any syntactically appropriate string, number, or other variable. Unlike normal syntactic variables, a metasyntatic variable stands for a value of any acceptable type. For example, foo in    dir foo ,  http://www.foo.com
FTP	file transfer protocol - a standard that defines how files are transferred over the Internet
Full duplex	flow of information in both directions at the same time
Gateway	a computer system that transfers data between otherwise incompatible networks
General rotation	random display of a banner advertisement on a site
GIF	graphics interchange format - originally created by CompuServe, it's now the most common format for compressed graphics on the Internet
Gopher	a menu based system for exploring the Internet
gTLD	generic top level domains - these include new domains such as .web .shop .firm .info .arts .rec .nom
GUI	guided user interface - the way you operate a program on your desk top, using devices such as toolbars, windows, menus and icons
Hit	an entry in the log file of a web server. A hit is generated by every request made to a web server. It has no predictable relation to users, visitors or pages
Host	a computer that enables users to communicate with other computers on a network
HTML	hypertext mark-up language - the set of mark-up symbols (tags) or codes inserted in a file intended for display on a web browser
HTTP	hypertext transfer protocol - an Internet protocol used on the WWW to transfer HTML files
Hub	a network device that distributes data to other systems on a network
Internet	a network of permanently connected networks linked by routers that use the TCP/IP protocals to communicate.
Internet Telephony	a cathegory of hardware and software that enables people to use the Internet as a transmission medium for telephone calls. For users with free or fixed price Internet access., Internet telephony software essentially provides free telephone calls to anywhere in the world. There are many Internet telephony applications available. Some, such as CoolTalk and NetMeeting, come bundled with popular web browsers. Others, are stand alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products
Internet2	is a research network for it's membership of over 150 US Universities, the US Government and some industry vendors. It's made up of two (now connected) networks, Abeline and Very High Performance Backbone Network Service (VBNS), which can only be accessed by fibre optic OC-3 (155Mbps) and OC-12 (622Mbps) respectively. It is generally considered as the prototype into which the web will develop to allow full speed interactive video etc.
InterNIC	the company that controls the registration of most domain names (.com, .org etc )
Intranet	a private network that works as an internal company wide Internet
Impression	relating to banner advertising - one display of the banner to a single viewer. Advertising rates are often related to the total number of times the banner is displayed
IP	Internet protocol - a protocol on which the Internet is based. A specification for the format of packets computers use when they communicate across the Internet (sometimes refers to the IP software a computer must run to communicate on the Internet).
IP Datagram	A packet of data sent across the interent. Each IP datagram contains the address of the computer that sent it, the IP address of the computer to which it's sent and the data being sent.
IPv6	Internet Protocal version 6 or next generation with 128 bit addresses. expected to become a standard in 2001.
ISDN	integrated services digital network - is a set of CCIT/ITU standards for digital transmission over ordinary telephone copper wire, as well as over other media. Home and business users who install ISDN adaptors (instead of their usual modems) can see highly-graphic web pages arriving very quickly (2 x 68k lines, up to 256k paired )
ISP	Internet service provider - any organisation offering connections to the Internet or to part of it whose service also generally includes hosting
Java	cross platform programming language used extensively on the net as it works on all computer systems. It can be used to create entire applications or to build small application modules or applets for use as part of a web page. Applets make it possible for the web page user to interact to interact with the page
JavaBeans	an object orientated programming interface from Sun Microsystems that enables you to build reusable applications or program building blocks called components, which can be deployed in a network on any major operating system platform
Javascript	an interpreted programming or script language from Netscape, the scripts of which are used extensively to make web pages 'dynamic'
JPEG	a bitmap file format (usually .jpg) for compressing and displaying images on the web
LAN	local area network - a computer network for a small area such as an office
Leased line	a permanent connection between two sites, which requires no dialling and includes all phone charges
Link validator	a program that tests and reports on the validity of the links on the pages in a web site. More advanced link validators test links to other web sites as well as links between pages on the same site
Linux	freely distributable implementation of UNIX that runs on a number of hardware platforms, including Intel and Motorola microprocessors. Because it's free, and it runs on many platforms, including PC's, Mac's and Amiga's. it's becoming popular
Log file analysis software	a log file records the following: the number of visitors (unique first time requests) to a home page the origin of the visitors in terms of their associated server's domain name(for example visitors from .edu .com .org and .gov sites and from online services) how many requests for each page at the site, which can be presented with the pages, with most requests listed first usage patterns in terms of time of day, day of week etc Analysis software takes this huge file and lets you view the findings in graph form, etc
Mail gateway	a machine that transfers mail between two or more e-mail systems
Media objects	files, other than HTML documents, that can be displayed or executed within HTML documents or in a stand alone fashion. Examples include GIF's,JPEG's, video, audio,PDF and Hot Java Applets
MSA	merchant service agreement - to do real time e-commerce online you will need a an MSA with a bank or credit card company
Meta tags	these are HTML tags that surround key words when submitting a site to a search engine
MIME	multipurpose Internet mail extensions - a method of sending binary objects by email
MP3	short for MPEG layer 3, this is a type of audio data compression than can reduce digital sound files by 12:1 ratio with virtually no loss in quality
MPEG	the standard for compressing audio and video files to send over the net
Multilink	the paring up of two ISDN connections for the transmission of a message unit
NNTP news server	network news transfer protocol - is the prevalent protocol for exchanging news on usenet newsgroups
OLR	offline reader - is a program that allows you to connect to an online system, download all your messages and email, read and reply to them offline and then send back your replies
PGP	pretty good privacy - a technique for encryption messages. PGP is one of the most common ways to protect messages on the Internet: because it's effective, easy to use and free. It is based on the public key method, which uses two keys. One is a public key that you disseminate to anyone from whom you want to receive messages. The other is a private key that you use to decrypt messages that you receive. To encrypt a message using PGP, you need the PGP encryption package, which is available free from MIT (the official repository)
PING	packet Internet groper - a program used to test destinations on the Internet to see if they exist, are operation and so on
Plug-ins	are programs that can easily be installed in a web browser to extend it's functionality
Polling	commecting to another system to check for email and messages
POP	post office protocol - email system with faster delivery than SMTP
Port number	Computers that run the TCP/IP protocols can use different ports to run different services
Portal	a new term for web sites that have all the services that people are likely to use on-line i.e search engines, chat rooms , online shopping etc
PPP	point-to-point protocol - this enables a computer to use TCP/IP with a standard telephone line
Protocol	standards governing the transfer of information between computers
Proxy server	a local server that acts as an intermediary between the user and the Internet, storing web sites and increasing security
Rot-13	a simple form of encryption, commonly applied to some usenet messages which rotates the alphabet 13 places forwards or backwards
Router	a system that transfers information between two networks using the same protocols
Server	a computer, or the software on that computer, that allows other computers to access via a network or over the Internet
Search Engine	a database of information on URL's linked to certain keywords. Internet users can use this data to find the information they need
SET	secure electronic connection - a new (1999) , more secure system for buying on-line with all transaction information encrypted, pioneered by visa and mastercard
SGML	standardised general mark-up language - An international standard notation used to define other mark-up languages. HTML and XML would be defined according to it's guidelines. It developed form the general mark-up language developed by IBM in the 1960's
Shockwave	a family of multimedia players that can be downloaded from macromedia.com or, more often now, are packaged with browsers that allow the viewing of shockwave files made with macromedia director and flash software.
Site	any of the individual networks that as a whole comprise the Internet
SLIP	serial line IP - is a protocol that enables a computer to use the Internet protocols using a standard telephone line
SME	small to medium sized enterprises with 20 to 500 employees
SMTP	simple mail transfer protocol - is used to transfer e-mail between computers, as part of the TCP/IP protocol family
SOHO	in information technology, SOHO is a term for a small office or home office environment
Spam	unwanted junk email
Spider	spiders are sent out by various search engines to search the web for information on web sites
SSI	server side includes - are commands that you give to your webserver by placing them right inside your HTML code! You can include a standard copyright disclaimer at the bottom of every page of your website, and if you need to change it, you only have to change it once!
SSL	secure socket layer - the encryption system built into web servers and browsers that uses 'certificates' of identity to authenticate web sites and surfers. These certificates are digitally signed and issued by a trusted third party such as VeriSign
Stat-tracking software	this is software that can be used to track useful information about when and where a web site is accessed and by whom
Streaming	video or audio files sent in compressed form over the Internet and displayed on the viewer's screen as it arrives
T1 Line	the T-carrier system, introduced by the Bell system in the US in the 1960's, was the first successful system that supported digitalised voice transmission. The original transmission rate (1.544 Mbps) in the T1 line is in common use today in ISP (Internet Service Provider) connections to the Internet
TCP	transmission control protocol - one of the protocols upon which the Internet is based. TCP handles the difficult task of ensuring that all the data arrives at the destination in the correct order.
TCP/IP	the basic communication language or protocol of the Internet (i.e. specifies how computers communicate on the internet)
Telnet	an Internet protocol that allows you to log in to other computer systems via the Net
TLD	top level domain - a top level domain such as .ie .com .org .net and .co.uk
Traffic	this is the term for the volume of hits a site receives
UNIX	an operating system that originated as an interactive time sharing system. It is commonly used by service providers and universities
URL	uniform resource locator - or the address given to files on the world wide web i.e http://www.ibm.com
Usenet	a group of systems that exchanges debate, chat, etc in the form of newsgroups across the Net
UUencode	a method of encoding binary data so that it can be sent as an ASCII file across networks by e-mail.A UUdecoder is required to convert the file back into executable binary file again
VBScript	an Internet version of visual basic developed by Microsoft and largely only supported by Microsoft's Internet Explorer browser
VeriSign	the leading provider of Public Key Infrastructure (PKI) and digital certificate solutions used by enterprises, web sites and consumers to conduct secure communications and transactions over the Internet
VRML	virtual reality modelling language- language for describing three dimensional image sequences and possible user interactions with them
WAN	wide area network as opposed to LAN (Local Area Network)
W3C	world wide web consortium - the governing and standards authority of the Internet W3C
WWW	world wide web - a html based information and resource system for the Internet
XHTML	extensible hypertext mark-up language - a synthesis of HTML 4.0 with XML which among other things will allow the introduction of new tags using XML's document type definitions (DTD).
XML	extensible mark-up language - that uses DTD's to define new tags thus allowing extensibility. Generally regarded as a more clearly defined than HTML and hence it's use in by newpapers etc for archiving information

Error codes help page back to pagetop

Connection Errors Invalid URL Invalid URL simply means that the format of the URL was invalid. The format should be in one of the following forms: http://www.someurl.com http://www.someurl.com/ http://www.someurl.com/page.jsp http://www.someurl.com/page.jsp?QueryString Host Not Found Host Not Found occurs when the web server's host computer could not be found using it's host/domain name (Fully Qualified Domain Name). This usually indicates a problem with your DNS system or connectivity to your DNS system or general Internet connectivity problems. Time Out A Time Out occurs when a the web server's host compter was found using it's host/domain name, but a connection could not be established within a predetermined set time. The default time out is set to 90 seconds. This usually indicates a problem with your routers or firewall, or a web server hardware failure, or general Internet connectivity problems. Connection Refused A Connection Refused error occurs when the web server's host computer is found, but the host computer refuses to accept the connection on the default port. This usually indicates a problem with your web server software or the web server software is not running. No Response from Web Server No Response from Web server occurs when the web server's host computer is found, and a connection is established to the default port. The request is sent to the web server, but it does not respond within a predertermined set time. This may indicate a problem with your web server software or backend systems or possibly an overloaded web server machine. Unexpected Error Unexpected Error occurs when our monitoring system encounters and error it can not classify into one of the categories above. This error is very rare.

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Web Server Status Codes/Messages The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. These codes are defined below. The Status Message is intended to give a short textual description of the Status-Code. 1xx: Informational - Request received, continuing process 2xx: Success - The action was successfully received, understood, and accepted 3xx: Redirection - Further action must be taken in order to complete the request 4xx: Client Error - The request contains bad syntax or cannot be fulfilled 5xx: Server Error - The server failed to fulfill an apparently valid request

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Informational 1xx This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. Since HTTP/1.0 did not define any 1xx status codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client except under experimental conditions. 100 Continue The client may continue with its request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server. The client SHOULD continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The server MUST send a final response after the request has been completed. 101 Switching Protocols The server understands and is willing to comply with the client's request, via the Upgrade message header field (section 14.41), for a change in the application protocol being used on this connection. The server will switch protocols to those defined by the response's Upgrade header field immediately after the empty line, which terminates the 101 response. The protocol should only be switched when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over older versions, and switching to a real-time, synchronous protocol may be advantageous when delivering resources that use such features.

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Successful 2xx All response codes that start with 2xx indicates that the request was successfully received, understood, and accepted. 200 OK The request has succeeded. 201 Created The request has been fulfilled and resulted in a new resource being created. The newly created resource can be referenced by the URI(s) returned in the entity of the response, with the most specific URL for the resource given by a Location header field. The origin server MUST create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server should respond with 202 (Accepted) response instead. 202 Accepted The request has been accepted for processing, but the processing has not been completed. The request MAY or MAY NOT eventually be acted upon, as it MAY be disallowed when processing actually takes place. There is no facility for re-sending a status code from an asynchronous operation such as this. The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the server persist until the process is completed. The entity returned with this response SHOULD include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the user can expect the request to be fulfilled. 203 Non-Authoritative Information The returned metainformation in the entity-header is not the definitive set as available from the origin server, but is gathered from a local or a third-party copy. The set presented MAY be a subset or superset of the original version. For example, including local annotation information about the resource MAY result in a superset of the metainformation known by the origin server. Use of this response code is not required and is only appropriate when the response would otherwise be 200 (OK). 204 No Content The server has fulfilled the request but there is no new information to send back. If the client is a user agent, it SHOULD NOT change its document view from that which caused the request to be sent. This response is primarily intended to allow input for actions to take place without causing a change to the user agent's active document view. The response MAY include new metainformation in the form of entity-headers, which SHOULD apply to the document currently in the user agent's active view. 205 Reset Content The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate another input action. The response MUST NOT include an entity. 206 Partial Content The server has fulfilled the partial GET request for the resource. The request must have included a Range header field (section 14.36) indicating the desired range. The response MUST include either a Content-Range header field (section 14.17) indicating the range included with this response, or a multipart/byteranges Content-Type including Content-Range fields for each part. If multipart/byteranges is not used, the Content-Length header field in the response MUST match the actual number of OCTETs transmitted in the message-body. A cache that does not support the Range and Content-Range headers MUST NOT cache 206 (Partial) responses.

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Redirection 3xx This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request. The action required MAY be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A user agent SHOULD NOT automatically redirect a request more than 5 times, since such redirections usually indicate an infinite loop. 300 Multiple Choices The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information (section 12) is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location. Unless it was a HEAD request, the response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice may be performed automatically. However, this specification does not define any standard for such automatic selection. If the server has a preferred choice of representation, it SHOULD include the specific URL for that representation in the Location field; user agents MAY use the Location field value for automatic redirection. This response is cachable unless indicated otherwise. 301 Moved Permanently The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD be done using one of the returned URIs. Clients with link editing capabilities SHOULD automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cachable unless indicated otherwise. If the new URI is a location, its URL SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s). If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued. Note: When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously change it into a GET request. 302 Moved Temporarily The requested resource resides temporarily under a different URI. Since the redirection may be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cachable if indicated by a Cache-Control or Expires header field. If the new URI is a location, its URL SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s). If the 302 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued. Note: When automatically redirecting a POST request after receiving a 302 status code, some existing HTTP/1.0 user agents will erroneously change it into a GET request. 303 See Other The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script to redirect the user agent to a selected resource. The new URI is not a substitute reference for the originally requested resource. The 303 response is not cachable, but the response to the second (redirected) request MAY be cachable. If the new URI is a location, its URL SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s). 304 Not Modified If the client has performed a conditional GET request and access is allowed, but the document has not been modified, the server SHOULD respond with this status code. The response MUST NOT contain a message-body. The response MUST include the following header fields: Date ETag and/or Content-Location, if the header would have been sent in a 200 response to the same request Expires, Cache-Control, and/or Vary, if the field-value might differ from that sent in any previous response for the same variant If the conditional GET used a strong cache validator, the response SHOULD NOT include other entity-headers. Otherwise (i.e., the conditional GET used a weak validator), the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers. If a 304 response indicates an entity not currently cached, then the cache MUST disregard the response and repeat the request without the conditional. If a cache uses a received 304 response to update a cache entry, the cache MUST update the entry to reflect any new field values given in the response. The 304 response MUST NOT include a message-body, and thus is always terminated by the first empty line after the header fields. 305 Use Proxy The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URL of the proxy. The recipient is expected to repeat the request via the proxy.

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Client Error 4xx The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents SHOULD display any included entity to the user. Note: If the client is sending data, a server implementation using TCP should be careful to ensure that the client acknowledges receipt of the packet(s) containing the response, before the server closes the input connection. If the client continues sending data to the server after the close, the server's TCP stack will send a reset packet to the client, which may erase the client's unacknowledged input buffers before they can be read and interpreted by the HTTP application. 400 Bad Request The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications. 401 Unauthorized The request requires user authentication. The response MUST include a WWW-Authenticate header field containing a challenge applicable to the requested resource. The client MAY repeat the request with a suitable Authorization header field. If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has already attempted authentication at least once, then the user SHOULD be presented the entity that was given in the response, since that entity MAY include relevant diagnostic information. 402 Payment Required This code is reserved for future use. 403 Forbidden The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable. 404 Not Found The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. If the server does not wish to make this information available to the client, the status code 403 (Forbidden) can be used instead. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. 405 Method Not Allowed The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an Allow header containing a list of valid methods for the requested resource. 406 Not Acceptable The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request. Unless it was a HEAD request, the response SHOULD include an entity containing a list of available entity characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice may be performed automatically. However, this specification does not define any standard for such automatic selection. Note: HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept headers sent in the request. In some cases, this may even be preferable to sending a 406 response. User agents are encouraged to inspect the headers of an incoming response to determine if it is acceptable. If the response could be unacceptable, a user agent SHOULD temporarily stop receipt of more data and query the user for a decision on further actions. 407 Proxy Authentication Required This code is similar to 401 (Unauthorized), but indicates that the client MUST first authenticate itself with the proxy. The proxy MUST return a Proxy-Authenticate header field containing a challenge applicable to the proxy for the requested resource. The client MAY repeat the request with a suitable Proxy-Authorization header field. 408 Request Timeout The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time. 409 Conflict The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that may not be possible and is not required. Conflicts are most likely to occur in response to a PUT request. If versioning is being used and the entity being PUT includes changes to a resource which conflict with those made by an earlier (third-party) request, the server MAY use the 409 response to indicate that it can't complete the request. In this case, the response entity SHOULD contain a list of the differences between the two versions in a format defined by the response Content-Type. 410 Gone The requested resource is no longer available at the server and no forwarding address is known. This condition SHOULD be considered permanent. Clients with link editing capabilities SHOULD delete references to the Request-URI after user approval. If the server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 (Not Found) SHOULD be used instead. This response is cachable unless indicated otherwise. The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time -- that is left to the discretion of the server owner. 411 Length Required The server refuses to accept the request without a defined Content- Length. The client MAY repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request message. 412 Precondition Failed The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server. This response code allows the client to place preconditions on the current resource metainformation (header field data) and thus prevent the requested method from being applied to a resource other than the one intended. 413 Request Entity Too Large The server is refusing to process a request because the request entity is larger than the server is willing or able to process. The server may close the connection to prevent the client from continuing the request. If the condition is temporary, the server SHOULD include a Retry-After header field to indicate that it is temporary and after what time the client may try again. 414 Request-URI Too Long The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret. This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long query information, when the client has descended into a URL "black hole" of redirection (e.g., a redirected URL prefix that points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present in some servers using fixed-length buffers for reading or manipulating the Request-URI. 415 Unsupported Media Type The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.

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Server Error 5xx Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable of performing the request. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. User agents SHOULD display any included entity to the user. These response codes are applicable to any request method. 500 Internal Server Error The server encountered an unexpected condition, which prevented it from fulfilling the request. 501 Not Implemented The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource. 502 Bad Gateway The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request. 503 Service Unavailable The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay may be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response. Note: The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers may wish to simply refuse the connection. 504 Gateway Timeout The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server it accessed in attempting to complete the request. 505 HTTP Version Not Supported The server does not support, or refuses to support, the HTTP protocol version that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client other than with this error message. The response SHOULD contain an entity describing why that version is not supported and what other protocols are supported by that server.

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