I was just working on my page when suddenly this error message popped up. Cant acces the site or wordpress. Have not done any changes in the code. Just uploaded som products. It worked again after about 15 minutes but why did I get this?

Server error!

The server encountered an internal error and was unable to complete your request.

Error message: 
Premature end of script headers: post.php

If you think this is a server error, please contact the webmaster.

Error 500