var img1 = new Image();
  	var img2 = new Image();
   	var img3 = new Image();
    var img4 = new Image();
	
	img1.src = "img/header05.jpg";
	img2.src = "img/header06.jpg";
	img3.src = "img/header07.jpg";
	img4.src = "img/header08.jpg";
	
	function imgDisp(){
		iValue = Math.random() * 4;
		rNumber = Math.ceil(iValue);
		if(rNumber==0)  rNumber++;
		document.image1.src = eval("img" + rNumber + ".src");
		}