Trying to convert position:absolute to "position:relative" (float:[left,right])

I am trying to convert a .CSS file to position divs in relative positions on the page (from absolute positions), but my form element is short (in height), whereas I want it to encompass the entire page. For this reason its contained divs are also short, as I'm using percentages for their height. How can I "grow" the form? My new .CSS is:

html
{
    background-color:Maroon;
    font:16px Bookman Old Style;
}

#form1
{
  height:100%; 
}

#div1
{
    float:left;
    width:100%;
    top:0%;
    height:20%;
    margin:15px;
    padding:10px;
    background-color:White;
}

#div2
{
    float:left;
    width:25%;
  ...