[an error occurred while processing this directive]

I got this error after installing drupal. The install process went well. But now I want to login as admin and I get this error: [an error occurred while processing this directive]

When I click on login: I get:

Not Found

The requested URL /user/login was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Some ideas? May I have problems with “clean urls?

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/1/feed