var img1ovr = new Image();
	img1ovr.src = "http://web.mit.edu/ist/images/header_start_ovr.gif";
	var img1off = new Image();
	img1off.src = "http://web.mit.edu/ist/images/header_start_up.gif";
	
	var img2ovr = new Image();
	img2ovr.src = "http://web.mit.edu/ist/images/header_service_ovr.gif";
	var img2off = new Image();
	img2off.src = "http://web.mit.edu/ist/images/header_service_up.gif";	
	
	var img3ovr = new Image();
	img3ovr.src = "http://web.mit.edu/ist/images/header_help_ovr.gif";
	var img3off = new Image();
	img3off.src = "http://web.mit.edu/ist/images/header_help_up.gif";
	
	var img4ovr = new Image();
	img4ovr.src = "http://web.mit.edu/ist/images/services_topic_ovr.gif";     
	var img4off = new Image();
	img4off.src = "http://web.mit.edu/ist/images/services_topic_up.gif";         
	
	var img5ovr = new Image();
	img5ovr.src = "http://web.mit.edu/ist/images/services_alpha_ovr.gif"; 
	var img5off = new Image();
	img5off.src = "http://web.mit.edu/ist/images/services_alpha_up.gif"; 
	
	var img6ovr = new Image();
	img6ovr.src = "http://web.mit.edu/ist/images/tab-viewmaclit.gif";
	
	var img7ovr = new Image();
	img7ovr.src = "http://web.mit.edu/ist/images/tab-viewwinlit.gif";
	
	var img8ovr = new Image();
	img8ovr.src = "http://web.mit.edu/ist/images/tab_serviceoverview_over.gif"; 
	var img8off = new Image();
	img8off.src = "http://web.mit.edu/ist/images/tab_serviceoverview_off.gif"; 
	
	var img9ovr = new Image();
	img9ovr.src = "http://web.mit.edu/ist/images/tab_servicedetail_over.gif"; 
	var img9off = new Image();
	img9off.src = "http://web.mit.edu/ist/images/tab_servicedetail_off.gif"; 
	
	var img10ovr = new Image();
	img10ovr.src = "http://web.mit.edu/ist/images/tab-viewlinlit.gif";
	
    var img11ovr = new Image();
    img11ovr.src = "http://web.mit.edu/ist/images/tab-viewpdalit.gif";