g1smd - 5:30 pm on Nov 14, 2006 (gmt 0)

It all depends what the specific URL represents.

If it is a URL that now redirects, is 404, or a domain that has expired, then Google will clean it up eventually.

If it is a URL that returns "200 OK" then it is likely that it is duplicate content, and the other URL that returns the same content is probably shown as a normal URL somewhere. The fix is to redirect all of the duplicates.

It might just be a "page with low PR" and poor linking from other sites, which some people report seeing in just the last few months.