var dragobjekt = null;
var dragx = 0;
var dragy = 0;
var posx = 0;
var posy = 0;

function draginit() {
  document.onmousemove = drag;
  document.onmouseup = dragstop;
}

function dragstart(element) {
  dragobjekt = element;
  dragobjekt.style.zIndex = 1000;
  dragx = posx - dragobjekt.offsetLeft;
  dragy = posy - dragobjekt.offsetTop;
}

function dragstop() {
	if(!isNull(dragobjekt)) {
		dragobjekt.style.zIndex = 100;
	}
	dragobjekt = null;
}

function drag(ereignis) {
  posx = document.all ? window.event.clientX : ereignis.pageX;
  posy = document.all ? window.event.clientY : ereignis.pageY;
  if(dragobjekt != null) {
    dragobjekt.style.left = (posx - dragx) + "px";
    dragobjekt.style.top = (posy - dragy) + "px";
  }
}