I became aware of an annoying little glitch on the Urban Mainframe yesterday. It seems that WordPress, on which this site is running, doesn't handle the URL http://example.com/index.html on an unmodified install (I've confirmed this on a handful of other WordPress sites). This is significant because index.html is a special file on many web-servers, often being the "home" page of a directory on the server. Without special handling, a request for index.html on a WordPress installation generates a 404 (file not found) error — which is obviously something we don't want our visitors to be presented with.

In my case the impact of the glitch was magnified because I employ a quite aggressive caching policy on this website — and yesterday an unlikely combination of factors resulted in my 404 error page replacing my home page for a complete cache cycle. It went something like this:

• cached "home" page expires
• next "home" page request is for http://urbanmainframe.com/index.html
• index.html file request results in a 404 error
• 404 error page is cached
• all subsequent requests for http://urbanmainframe.com/ — and other "home" page URLs — return the cached 404 error page until the cache is next invalidated

Quite a serious glitch then!

There are two things that shouldn't have happened here.

1. Requests for index.html should not result in 404 errors.
2. Error pages should never be cached.

I resolved the first issue by adding the following snippet of code to the very beginning of the 404.php file in my WordPress theme:

<?php
if ($_SERVER['REQUEST_URI'] == '/index.html') { header("Location: http://urbanmainframe.com/"); exit; }
?>

For the second issue I've filed a bug report with the authors of W3 Total Cache, which is the caching system I use here on the Urban Mainframe.