how to make a full screen div, and prevent size to be changed by content?

for my web application, i would like the main div to be full screen (both width and height = 100%), and regardless of content, i want it to stay at that size. that means, if there are not much content, it shouldn't shrink, and if there are too much content, it shouldn't push this main div.

how can i do this?

(i'm ok with hacks applied to this div, as long as it will keep contents hack-free)

Or even just:

<div id="full-size">
  Your contents go here
</div>

html,body{ margin:0; padding:0; height:100%; width:100%; }
#full-size{
  height:100%;
  width:100%;
  overflow:hidden; /* or overflow:auto; if you want scrollbars */
}

(html, body can be set to like.. 95%-99% or some such to account for slight inconsistencies in margins, etc.)

#fullDiv {
    height: 100%;
    width: 100%;
    left: 0;
    top: 0;
    overflow: hidden;
    position: fixed;
}