var minY;
var maxY;
function onPageScroll () {
 // var pushDiv = document.getElementById ("pushDiv");
  //pushDiv.innerHTML = getScrollPosY ();
  // ----
  var mainLeftDiv = document.getElementById ("mainLeftDiv");
  var currentScrollY = getScrollPosY ();
  if (currentScrollY > minY) {
    mainLeftDiv.style.marginTop = currentScrollY - minY + "px";
    if (currentScrollY > maxY) {
      mainLeftDiv.style.marginTop = maxY - minY + "px";
    }
  } else {
    mainLeftDiv.style.marginTop = "0px";
  }
}
function sideScrollInit () {
  var mainLeftDiv = document.getElementById ("mainLeftDiv");
  var mainRightDiv = document.getElementById ("mainRightDiv");
  // ---
  minY = mainLeftDiv.offsetTop;
  maxY = (mainRightDiv.offsetHeight - mainLeftDiv.offsetHeight) + minY;
  onPageScroll ();
}
function getScrollPosY () {
  var x,y;
  if (self.pageYOffset) // all except Explorer
  {
	 // x = self.pageXOffset;
	  y = self.pageYOffset;
  }
  else if (document.documentElement && document.documentElement.scrollTop) // Explorer 6 Strict
  {
	  //x = document.documentElement.scrollLeft;
	  y = document.documentElement.scrollTop;
  }
  else if (document.body) // all other Explorers
  {
	 // x = document.body.scrollLeft;
	  y = document.body.scrollTop;
  }
  return y
}