just another blank everything post

hi
i was working on two files: style.css from the theme folder and the widgets.php form the wp-includes.

while uploading them i clicked somewhere else in the admin and refreshed the homepage.

everything is blank. i tried everything i could find around but before i delete and reinstall wp can someone help me in another way maybe. i am sure its not big. but i dont know from where to solve it.
thanks
C