Post-new.php is broken

I was trying to add some text to my post-new.php as a reminder to me when I’m writing articles. So I added document.write("test"); in the post.php and now when I go to the post-new.php it loads then goes to a blank page with the text “test” and I can’t do anything. So then I downloaded wordpress 2.6 again and replaced the whole wp-admin folder. Didn’t work. So I reinstalled wordpress 2.6. Didn’t work. Then I deleted wp-admin then put back the original. Didn’t work. At this point I’m thinking I should delete my wordpress installation and reinstall, or it is something in my SQL server but I doubt it. Please help.