I added height: 100%; to the html tag and suddenly it almost works.
The footer gets pushed down a little bit too far, resulting in a vertical scrollbar appearing. See for yourself here.
My margin on the wrapper div is -50px, push is 50px and footer height is 50px.
I cleaned my code thoroughly and replaced all margins with padding, I have no clue why the footer is pushed down too far.
I got rid of the scrollbar by reducing the height of the footer to 26px – then it all works perfectly, but I’m really not sure what will happen when I keep adding elements to my page. I would like it to work how it is supposed to, so that I don’t have to change the footer height all the time.