In my description of the problem it was not clear. Let me try again.
NB. This is a problem that is characteristic of my production, creation, and development sites (not only for my site, as commentators seem to think).
NB. This issue occurs when using Chrome, not Firefox.
The problem occurs on the home page of the site: http://www.example.com (or with "/index.php appended"). The page loads successfully, but the Chrome Developer Tools console panel shows a 404 error. The message reads "GET http: //www.example/undefined 404 (not found)". It always shows an error, as in "(index): 1", which is a DOCTYPE line. Whatever the problem is, it is not.
The page loads fine, I just get this odd message in the Developer Console. (I probably did not quite understand this in the original description of the problem.) The Firfox console does not detect such an error.
I want to track what causes this error. In particular, I would like to find where Chrome gets the "undefined" URL. My hunch (but just an assumption) is that one of my many Javascript files extracts a URL from an undefined variable. Chrome location of the problem, "(index): 1", this is incorrect. I would appreciate any ideas on how to get a more useful error message from Chrome: the name of the file in which the URL was found will help. If I can do this without setting breakpoints in all Javascript files one by one, that would be especially nice. :-)
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