I think I have screwed up my permissions in Ubuntu.

I am using my server to run PHP. I recently ran across a problem where PHP could not create directories in the var/www-directory, so I searched around on the internet. Now PHP can write and access anything like it should, but as a user, I can't create new folders or files anymore.

Right now, the permissions for folders are like this:

drwxrwsr-x 2 www-data www-data [Folders]

This is the permissions when I upload using sftp:

-rw-rw-r-- 1 gautvedt www-data [Folders]

What have I done wrong and how can I change this?