Any mix of upper and lower case makes for a "different" URL, as you probably know. Troubles can come from any server (IIS for a major example) that is not case sensitive. Googlebot does several kinds of "safety checks" for common server errors these days - your #1 would line up with that.

Make sure that all links on the site, and in any sitemap, all use consistent case.

If possible, always use all lower case for everything.

I can't think of any logical reason Google would attempt to spider variations on a URL. More likely someone has linked to the site using lowercase instead of mixed case. In my experience this is fairly common.

More likely someone has linked to the site using lowercase instead of mixed case. In my experience this is fairly common.

This is one of several good arguments for using all lower case in the first place.

Well, our back end programmer has done the following:

I just installed an Apache module called mod_speling (that's the correct spelling of it, it's a joke) that makes Apache be case-insensitive, and recovers from minor misspellings (omitted/added characters, transposed characters). That now makes all those lower-case URLs reachable.

As opposed to making all of the URL's have a lower case naming structure. Will this Apache module resolve the problems I'm having?

The spec on this module says:

If, after scanning the directory,

no matching document was found, Apache will proceed as usual and return a "document not found" error.

only one document is found that "almost" matches the request, then it is returned in the form of a redirection response.

more than one document with a close match was found, then the list of the matches is returned to the client, and the client can select the correct candidate.

[httpd.apache.org...]

My concern is that the redirection response returns a 301 status code and not a 302. A 302 would open you up to serious duplicate url problems. Remember, Google IS case sensitive, as are all the major search engines.

mod_speling uses permanent redirects.

Thanks, Andy, I should have known better. We're talking about Apache here, not some IIS oddity.

As opposed to making all of the URL's have a lower case naming structure. Will this Apache module resolve the problems I'm having?

Sounds like it will, Propools.

Thanks to all.

One thing to watch with mod_speling is that it doesn't work with mod_rewritten URLs.

Some very careful testing is in order here then.

You'll need a variety of test URLs with a mixture of case types, and some way to see the indvidual HTTP headers (WebBug or Live HTTP Headers, or some online tool).

Thanks g1smd, I'll check them out.