404 to sites/default/files/css/, I have a site that has a 404 being reported as "sites/default/files/css/," - yes, a css file with the name comma ","

I have no idea what is causing this 404.  The watchdog shows the referring URL can be almost any page on the site but going there and viewing the page source does not turn anything up.  It is intermittant and not created on every page request.

Has anyone seen this before? Anyone know what causes it?

I am using Drupal 7.14

Kind regards,

John
Assuming everything is using proper Drupal methods for attaching stylesheets (.info, drupal_add_css, $foo["#attached"]["css"], etc), I think it is impossible for core to create a bad link to a file.  Still, it would be worth it to search the code for "drupal_add_css" and "#attached" to see if there are any problems.

I think there are two possibilities here.

One could be a JS library dynamically attaching a stylesheet to the page.  Unless you are doing this yourself, I don't think this is a likely culprit.  Most of the libraries that do this (eg, jQUery UI) are rather well tested and I doubt would do this.  Stranger things have happened, though.

The other possibility is a bad url() reference in your CSS for a font or background image.  Search though all of your CSS for "url" and see if you have any problems.  Validating the CSS couldn't hurt, either.