maintain div scrollbar position

The key is document.getElementById("yourdiv").scrollTop

function getScrollXY() {
   document.getElementById("scroll_position").value = document.getElementById("screenDiv").scrollTop;
}         
function setScrollXY() {
   var pos = document.getElementById("scroll_position").value;
   var objDiv = document.getElementById("screenDiv");
   objDiv.scrollTop = parseInt(pos);
}