var changeBG = function() {
	var rndnum=Math.floor(2*Math.random())
	switch (rndnum) {
		case 0:
		document.getElementById('top').style.background = '#ffffff url(images/issrl_header_1.jpg) no-repeat top right';
		break
		case 1:
		document.getElementById('top').style.background = '#ffffff url(images/issrl_header_2.jpg) no-repeat top right';
		break
              default:	// For completeness, but not used.
		document.getElementById('top').style.background = '#ffffff url(images/issrl_header_1.jpg) no-repeat top right';
	}
}
if (window.addEventListener)
	window.addEventListener("load", changeBG, false);
if (window.attachEvent)
	window.attachEvent("onload", changeBG);