if (document.images) { 
	  img1on=new Image();
  	img1on.src="images/topnav_contact_on.gif";
		img2on=new Image();
    img2on.src="images/topnav_sitemap_on.gif";
    
    
    img1off=new Image();
    img1off.src="images/topnav_contact_off.gif";
    img2off=new Image();
    img2off.src="images/topnav_sitemap_off.gif";
		} 

function imgOn(imgName) { 
   if (document.images){ 
   document[imgName].src = eval(imgName + "on.src"); 
    } } 
function imgOff(imgName) { 
   if (document.images) { 
   document[imgName].src = eval(imgName + "off.src"); 
    } }