Apache, as probably most Web servers, have this feature where it will show an HTML formatted list of the files and directories under a given directory if no so called “index” files was provided, through its
autoindex module; while it can prove handy, especially when used with the HeaderName and ReadmeName directives, it has a major drawback: its output is not HTML valid!
Even though the code sets a proper doctype, it uses the
<img> tag inside a
<pre> elements, which is not allowed in HTML 3.2 (nor in the following versions):