var xPos_fly = 300;
var yPos_fly = 200; 
var step_fly = 1;
var delay_fly = 30; 
var height_fly = 0;
var Hoffset_fly = 0;
var Woffset_fly = 0;
var yon_fly = 0;
var xon_fly = 0;
var pause_fly = true;
var interval_fly;
var img1_fly = document.getElementById("img123");
img1_fly.style.top = yPos_fly;
function changePos() 
{
	width_fly = document.body.clientWidth;
	height_fly = document.body.clientHeight;
	Hoffset_fly = img1_fly.offsetHeight;
	Woffset_fly = img1_fly.offsetWidth;
	img1_fly.style.left = xPos_fly + document.body.scrollLeft;
	img1_fly.style.top = yPos_fly + document.body.scrollTop;
	if (yon_fly) 
		{yPos_fly = yPos_fly + step_fly;}
	else 
		{yPos_fly = yPos_fly - step_fly;}
	if (yPos_fly < 0) 
		{yon_fly = 1;yPos_fly = 0;}
	if (yPos_fly >= (height_fly - Hoffset_fly)) 
		{yon_fly = 0;yPos_fly = (height_fly - Hoffset_fly);}
	if (xon_fly) 
		{xPos_fly = xPos_fly + step_fly;}
	else 
		{xPos_fly = xPos_fly - step_fly;}
	if (xPos_fly < 0) 
		{xon_fly = 1;xPos_fly = 0;}
	if (xPos_fly >= (width_fly - Woffset_fly)) 
		{xon_fly = 0;xPos_fly = (width_fly - Woffset_fly);   }
	}
	
	function start_fly()
	 {
	 	img1_fly.visibility = "visible";
		interval_fly = setInterval('changePos()', delay_fly);
	}
	function pause_resume() 
	{
		if(pause_fly) 
		{
			clearInterval(interval_fly);
			pause_fly = false;}
		else 
		{
			interval_fly = setInterval('changePos()',delay_fly);
			pause_fly = true; 
			}
		}
	start_fly();