geekgyan on "Please help site not loading"

I got an email from clef saying 'Clef’s logout hook [1] for Geek Gyan is currently failing'. Logout hook ERROR: 500 Server Error: Internal Server Error for url.
i searched and found out that its because of server side error,if iam not wrong.
i dont know what went wrong.My site is http://www.geekgyan.com i tried disabling plugins using filezilla but w3tc gives an error and instruct to delete me db.php but when i do so and try to acces admins panel an another error pops up saying 'Your PHP installation appears to be missing the MySQL extension which is required by WordPress.'
i tried calling godady they said its not from theres side.
Also i noticed that there is .htaccess.bak file but no .htaccess file.
Thanx in advance :)