For those who encounter this weirdo on their self-hosted WordPress blog!
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, email@example.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
I tried disabling some new plug-ins etc but nothing helped.
Eventually found that the index.php file had all its permissions as 000. Some sites mentioned that this could be an issue.
Using the cPanel, I navigated to the index.php file of my wordpress installation folder and set permissions to be 755.
With that my site was back up again! Also I could access the administration portion of the site even when the blog itself was down!!