TOTAL MELTDOWN!!!

i tried loging into my blog https://www.wikiweblog.com/wp-admin and the page isn’t even there. Please tell me what I need to do. If you go to that link you’ll see a message that reads:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [email protected] 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 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request

I DON’T KNOW WHAT THAT MEANS!!! EVEN MY TEMPLATE IS MISSING. The last thing I remember doing was changing the url name from “www.wikiweblog.com” to “www.wikiweblog.com/home”. How do i fix this??