Maybe a temporary problem with your ISP. Try pinging to the GMail servers.
Also you can try Proxify at
http://proxify.com to access GMail. Just remember to use
http://gmail.google.com/gmail/ as the URL to GMail (to avoid redirection). If you can see the homepage of GMail, it is available and working. Unfortunately you will not be able to log in, because of the protections made by Proxify.