What does it do?
Detects missing files within this website, i.e. files which pages require to load completely that are missing.
Why is it important?
Broken files usually mean part of a webpage is missing or broken, like so:
Some broken files aren’t noticeable to the user, as the missing file may not be used in a way that is obvious. For example, a background image might be missing, but a plain background might still appear ok. These broken files are still an issue however, as they slow down the webpage from loading; the missing files must be unnecessarily requested and rejected by the webserver.
How is it measured?
Sitebeam looks at every file used by every webpage, and identifies any files which they use. Note this includes files which comprise a webpage (e.g. images or stylesheets) but not files which are linked to directly as download (e.g. Word documents or PDFs). Those files would be discovered by the Broken links test.
Files are marked as broken but are not
Check the HTTP code which was returned by the file. If no HTTP code was returned, this means Sitebeam could not get a response from the server at the time it was testing. Sitebeam tries each failed file twice: it is possible the site did not respond or was heavily loaded. If a HTTP code was returned, that code should reveal the nature of the problem: for example a 500 error would indicate the server was having an internal problem at the time.
A missing file was not detected
Sitebeam can only find files used by pages it tested. Ensure that the relevant page(s) were being spidered by Sitebeam first.
You can see exactly what Sitebeam sees to diagnose any further problems.
How to improve this score
Fix any broken files. Either remove the file because it is not needed, update the link to point to the correct location or replace the missing file with the correct content.