can't access web site or wp-admin, "internal server error"

My web site southasiahand.com was working fine this afternoon, and I used wp-admin yesterday. This evening, I got an error message from both:
“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator 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.
________________________________________
Apache Server at southasiahand.com Port 80″

What can I do? who and where is the server administrator? Help!!