Server Error when trying to click any link or preview any site other than the home page

I installed everything on my server and everything seems to work as expected. I can edit the page in the editor and all the sub pages, too. But when I preview the homepage none of the links work. I can see the homepage but when I click on a link to a subpage I get this error:

"Internal Server Error

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

Please contact the server administrator at to inform them of the time this error occurred, and the actions you performed just before this 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."

When I try to preview one of the subpages directly I get the error right away. It seems like only the Homepage works (and the "under construction" page).