wp-admin shows blank page, how to fix it?

Question

I am working with WordPress 3.5.8. Yesterday I made some changes into it to a friend. I don\'t know what happened, but after some time when I try to log in at wp-admin side and

Answer 1

I had this problem (not showing /wp-admin/), when I moved my site to new host. i solve this problem by: 1. Re mane activated theme's folder 2. Install that them again and active it 3. copy and re place some customized file like .css .js from backup

Now problem solved.