Dead link
A dead or defective reference ( link ) or dead link is a hyperlink on the World Wide Web that points to a resource (such as a website or file ) that does not (or no longer) exist . When calling the URI , the web server usually returns a response with the HTTP status code 404 Not Found (the requested resource could not be found) or 410 Gone (the resource no longer exists).
References to non-existent passages are also known from printed reference works .
causes
Dead links are a hitherto unsolved problem of hypertext and, at its core, stem from the fact that the Internet is a decentralized network . Therefore, its integrity can never be guaranteed.
The reasons for the existence of dead links can be very different and, above all, occur in very different places. Reasons that are frequently encountered in practice include:
- The file referenced by the URL has been moved, renamed, or deleted.
- The link on the original page is specified incorrectly, for example in the upper or lower case in the path (URIs are case sensitive in certain places ).
- The domain you are looking for has just been assigned to a registrar and the website itself still has no content.
- The web server is not (or no longer) accessible, for example due to network problems or because the computer is switched off.
- The host or domain name does not exist (anymore) or cannot be resolved in DNS .
The respective creators of the website are responsible for errors in internal links. If the system (e.g. in a content management system ) does not automatically display the dead links, they can be tracked down with the help of tools. [1]
impact
The problem with URLs that no longer exist is mainly due to the fact that the linking pages are not or cannot be informed of the non-existence. This applies in particular to external links that are in another domain . Search engines in particular have often indexed websites that have not existed for weeks or months. Some search engines will continue to cache the content for some time .
Dead links also affect the quality of search results in search engines. In some PageRank calculation methods , a method introduced by the search engine operator Google for determining the quality of websites, dead links play a role (solving an eigenvector problem ) and are first removed before the calculation. However, they are usually reinserted in the last step of the numerical iteration process, so that a PageRank is also assigned to these pages.
The English term link rot (roughly: "link rotting") has become established for URLs becoming invalid over time. There are various estimates of the extent: A study of digital libraries revealed that around 3% of the objects were no longer accessible after a year. [2] The bookmarking website Pinboard reported in 2014 that it was observing a fairly stable linkrot rate of 5% per year. [3]
possible solutions
According to a Harvard study, as early as 2013, fifty percent of the links cited by the American Supreme Court no longer referred to the original information. A solution could lie in the "perma.cc" service offered by Harvard University, which stores scientific Internet sources. [4] Another option, though one that tends to combat the symptoms of broken links, is the Internet Archive 's Wayback Machine . Chronological copies of websites allow access to websites that no longer exist in the original for a long time.
On the other hand, committees such as the W3C are fighting the cause with the Cool URIs don't change campaign [5] , which is intended to raise awareness of the need for fixed URLs among the creators and administrators of websites. One solution is to use dynamic linking, e.g. B. subdomains or directory names can be used. In addition, there are already systems that track the destination of fixed URLs by automatically creating a redirect , such as through a Persistent Uniform Resource Locator .
Origin of the error code "404"
The error code "404" is said to have arisen because in the early days of the Internet, the server that caused this error due to missing files was in room 404 at CERN , where the origin of the World Wide Web can be found. However, this story is classified as a modern saga and goes back to a hoax . [6] [7] In reality, the error code is not based on any living story like this one, but is just one error code among 27 different ones that are defined as “ client errors ” in the HTTP standard. [8th]All HTTP status codes have three digits, client error status codes start with the digit "4", so "404" is the fifth registered client error.
trivia
In 2007, in Nagoya , Japan , an emo band named itself after the error code: 404 Not Found .
See also
- Hanging pointer as a general concept in computer science
web links
- w3.org - Status Code Definitions - Status code definition
itemizations
- ↑ Heise RegioConcept March 22, 2017: Every dead link is a small nail in the coffin for your website! , retrieved September 7, 2017
- ↑ Michael L Nelson, B Danette Allen: Object Persistence and Availability in Digital Libraries . In: D-Lib Magazine . 8, No. 1, 2002. doi : 10.1045/january2002-nelson .
- ↑ Maciej Cegłowski: Web Design: The First 100 Years September 9 , 2014. Retrieved July 22, 2015.
- ↑ What to do with dead links? Archive for online quotes, In FAZ from September 30, 2020
- ↑ http://www.w3.org/Provider/Style/URI (English)
- ↑ Story of 404. In: plinko.net. Retrieved 7 June 2018 .
- ↑ HTTP/1.0 Room 404 Object Not Found. In: room404.com. Retrieved 7 June 2018 .
- ↑ Anna Wiener: Page not found: a brief history of the 404 error. In: Wired.com. 12 April 2017, retrieved 6 June 2018 .