footer with absolute position - responsive design

i have a little problem with my responsive design. I am using a normal with this css.

footer {
width: 100%;
height: 20px;
position: absolute;
bottom: 5px;
left: 0;
}

It works perfekt. When i am using a smaller screen i have to scroll. Thats normal.

The problem is, that the is not at the bottom. It is in the middle of the screen. Like margin-top:100% of the full screen, without scrolling.

I hope you understand what i mean :)

Thanks!