Website URL:  

• It tries to diagnose the common www vs non-www duplicate content issue by checking the headers returned by both versions of the url, the current cache in google, and possible PR dispersion.
• It checks for the common default page error where both the / and /index.html (or other default page) return 200/OK headers.
• It checks for incorrect 404 pages which deliver a 200/OK Header and,
• It checks for supplemental pages in the Google index.