How can I force my footer to stick to the bottom of any page in CSS?

Question

This is my code:

#footer {
   font-size: 10px;
   position:absolute;
   bottom:0;
   background:#ffffff;
}

I\'ve no idea what is wrong with

Answer 1

#footer { clear:both; position:fixed; width:100%; height:50px; bottom:0; background:black;}