editing errors?

When ever I select to “customize” my theme, I get the following error:

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.

Also, when ever I go to “view” my webiste, i get “revolutionary slider error: slider with alias home-special cannot be found”. I imported the demo but still get this error