I assume you are having some padding issues, with stuff being pushed out diferently across diferent browsers - plz consider formulating your question a bit better.
But heres a sure way to fix the majority of padding issues when working with 100% height
html,body,form{
padding: 0 0 0 0;
margin:0 0 0 0;
width:100%;
height:100%;
}
hope this helps