window.onload = function(){
	document.onmousemove = doDrag;
	document.onmouseup = stopDrag;
	}	

/* object drag */

var dragObj = 0;
var mousePos = 0;

	
function startDrag(obj_id){
  dragObj = document.getElementById(obj_id);
	isDrag = 1;
	}
	
function doDrag(ev){
	newMousePos = mouseCoords(ev);		
	if (dragObj){
		dragObj.style.left = (dragObj.offsetLeft + newMousePos['x'] - mousePos['x'])+'px';	
		dragObj.style.top = (dragObj.offsetTop +  newMousePos['y'] - mousePos['y'] )+'px';
		}
	mousePos = newMousePos;
	}
	
function stopDrag(ev){
	dragObj = 0;	
	}
	
function mouseCoords(ev){
	if(!ev) ev = window.event;
	if(ev.pageX || ev.pageY) return {x:ev.pageX, y:ev.pageY}
	return {
		x:ev.clientX + document.body.scrollLeft - document.body.clientLeft,
		y:ev.clientY + document.body.scrollTop  - document.body.clientTop
		}
	}