Approaches To Link Checking
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There are several reasons why it is important to ensure that links on Web sites work correctly:
However there are resource implications in maintaining link integrity.
A number of approaches can be taken to checking broken links.
Note that these approaches are not exclusive: Web site maintainers may choose to make use of several approaches.
There is a need to implement a policy on link checking. The policy could be that links will not be checked or fixed - this policy might be implemented for a project Web site once the funding has finished. For a small-scale project Web site the policy may be to check links when resources are added or updated or if broken links are brought to the project's attention, but not to check existing resources - this is likely to be an implicit policy for some projects.
For a Web site one which has a high visibility or gives a high priority to the effectiveness of the Web site, a pro-active link checking policy will be needed. Such a policy is likely to document the frequency of link checking, and the procedures for fixing broken links. As an example of approaches taken to link checking by a JISC service, see the article about the SOSIG subject gateway [1].
Experienced Web developers will be familiar with desktop link-checking tools, and many lists of such tools are available [2] [3]. However desktop tools normally need to be used manually. An alternative approach is to use server-based link-checking software which send email notification of broken links.
Externally-hosted link-checking tools may also be used. Tools such as LinkValet [4] can be used interactively or in batch. Such tools may provide limited checking for free, with a licence fee for more comprehensive checking.
A popular approach is to make use of SSIs (server-side includes) to retrieve common features (such as headers, footers, navigation bars, etc.). This can be useful for storing HTML elements (such as the DOCTYPE declaration) in a manageable form. However this may cause validation problems if the SSI is not processed.
Another approach is to use a browser interface to tools, possibly using a Bookmarklet [5] although UKOLN's server-based ,tools approach [6] is more manageable.
It is important to ensure that link checkers check for links other than <a href=""...> and <img src="...">. There is a need to check external JavaScript, CSS, etc. files (linked to by the <link> tag) and that checks are carried out on personalised interfaces to resources.
It should also be noted that erroneous link error reports may sometimes be produced (e.g. due to misconfigured Web servers).
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Web page by Brian Kelly of UKOLN.
Last Modified 7-October-2005
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