Problem with Studio 404 errors


I have been having difficulties with Studio generating perpetual 404 errors on my site ( With some help from programming friends, I think the problem is originating with a call that leads to this html:

<link media="all" type="text/css" target="_blank" href="" rel="stylesheet">

Every time it tries to the pull the default.css file it generates a 404 error, and then the 404 error.php scripts generate the same 404 error, etc. etc. This cascading error problem is rapidly filling up my error log and causing the site to crash.

I'm quite a novice at all of this, so any help/insight would be appreciated!

Stephanie H.