var xpos = 300;
var ypos = 200; 
var step = 1;
var delay = 30; 
var height = 0;
var hoffset = 0;
var woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
img1.style.top = ypos;
function changepos() 
{
	width = document.body.clientwidth;
	height = document.body.clientheight;
	hoffset = img1.offsetheight;
	woffset = img1.offsetwidth;
	img1.style.left = xpos + document.body.scrollleft;
	img1.style.top = ypos + document.body.scrolltop;
	if (yon) 
		{ypos = ypos + step;}
	else 
		{ypos = ypos - step;}
	if (ypos < 0) 
		{yon = 1;ypos = 0;}
	if (ypos >= (height - hoffset)) 
		{yon = 0;ypos = (height - hoffset);}
	if (xon) 
		{xpos = xpos + step;}
	else 
		{xpos = xpos - step;}
	if (xpos < 0) 
		{xon = 1;xpos = 0;}
	if (xpos >= (width - woffset)) 
		{xon = 0;xpos = (width - woffset);   }
	}
	function start()
	 {
	 	img1.visibility = "visible";
		interval = setinterval('changepos()', delay);
	}
	function pause_resume() 
	{
		if(pause) 
		{
			clearinterval(interval);
			pause = false;}
		else 
		{
			interval = setinterval('changepos()',delay);
			pause = true; 
			}
		}
	start();