Next Link Misleads Logs

Relates to Web Standards and Accessibility, Apache, Firefox and Co

This is a very annoying quirk that took me far too long to track down! When calling pages on my test platform using a new caching system and a package of builder classes for parsing XML based metadata a second call for a page was being made to the server. In short, the page in question was that defined as next in the relative links:

<link rel="next"
           href="/uri_of_page/"
           title="Description of the page/>

At first I thought this was down to a coding error in one of the PHP classes. Fortunately browsing the HTTP headers and a timely flick through the HTML 4.01 Specification abated my growing frustration. The specification states the following for the next link type:

Refers to the next document in a linear sequence of documents. User agents may choose to preload the "next" document, to reduce the perceived load time. http://www.w3.org/TR/html401/types.html#type-links

Well it is the second sentence that is clearly significant here. The second call for a page to the server abides to the above recommendation. In fact on further scrutiny I discovered this problem is distinctive to Mozilla family which utilise the link toolbar (I did not take further time out to test on Opera).

I see a major conflict in this. The relative links have been adopted as important elements for accessible navigation and are a recommended technique for achieving several guidelines in the WCAG at level 2 and 3. Yet, as long as user-agents abide to the above statement regarding the next link type, there is a conflict of interest between attaining accessibility and maintaining reliable web server logs! This is especially so with Webalizer, the most popular open source software for producing tabular and graphical statistics from Apache's Common Logfile Format. For each pre-loading call to the webserver will register an additional page hit for that page in the access log. If the user actually visits the page via the next link a second page impression will be registered!

Fortunately for once, Exploder is beneficial here, since it has no idea whatsoever about relative links, and therefore the above over-logging will not occur. Sadly this may explain why on a number of my clients sites (this site included) Mozilla and co are falsely striving into the lead on the browser stakes! One solution may be to flush out the pre-loading entries by looking for calls for two separate pages from the same IP address within a second or two of each other. If I can find a minute may call for some Awk and Sed.

Posted on Saturday, May 22, 2004 at 00:42:26.

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