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Link rot — sometimes spelled linkrot — describes the way in which links to web pages routinely decay or become unavailable over time. For the average programmer, citing a website doesn't necessarily mean the link will stay active forever. Most people searching a site get frustrated when they click links only to find they don't exist, and examples of link rot can be found in a variety of sources. Rot can occur on any kind of website, but broken links that occur in things like scholarly publications can lead to a failure to link to cited sources, which may diminish the scholarly value of a paper.
One trouble with link rot is that some large sites like newspapers routinely move links to new addresses and don't always leave a connection to them; alternately, they may charge money for articles that were once available for free, as soon as they are archived. This can mean initial links take people to a different location, simply no longer work, or limit access to paying customers. For those conducting research on the Internet, getting stopped by requests for payment or broken links can be very frustrating.
The amateur programmer with a few web pages can easily get rid of link rot by checking links once a month or so to make sure none are broken, and correcting those that are. This strategy doesn't work well for people with large numbers of pages and outbound links or even just a page or two with multiple citations. There are some other strategies to help diminish this problem, however.
For large numbers of pages, programmers may use special computer applications called content management systems, which help check all links for potential link rot. These programs don't always work because some links to sites may not contain the same material anymore. This is common when people use the practice of deep linking, where they link not to the site's front page, but to some specific page within the site, which may easily get an address change later on. Programmers often avoid deep linking when they have numerous outlinks.
Another way to combat the issue of link rot is to create permalinks, which create a permanent and accessible version of unique content. This is especially common with blog entries, where the material of a single blog doesn't stay on the front page for long, and will be moved after a certain time. Alternately, there are now many archives available which help create copies of unique content on web pages so that it will remain accessible forever. Linking to archived material or creating an archive of linked material can prevent or reduce link rot.
There is also the possibility that link rot can affect a site's ranking, which can matter when people want to create high profile pages. More often, the ranking of web pages is diminished if they change addresses of key material and don't inform people who have created inlinks to their page. Programmers who move material should create redirects that will shunt people arriving at the page from a link to the new address. These are called 301s, and it is worthwhile for site owners to know how to create and use them to avoid losing potential new visitors to a site due to a new address.