if(document.images)
	{
		
		a1 =  new Image();
		a1.src = "images/header1.jpg";
		
		a2 =  new Image();
		a2.src = "images/header2.jpg";
		
		a3 =  new Image();		
		a3.src = "images/header3.jpg";
		
		a4 =  new Image();		
		a4.src = "images/header4.jpg";
		
	}