if (document.images) {

aboutoff=new Image();
aboutoff.src= "images/menu/aboutoff.gif";
abouton=new Image();
abouton.src= "images/menu/abouton.gif";
homeoff=new Image();
homeoff.src= "images/menu/homeoff.gif";
homeon=new Image();
homeon.src= "images/menu/homeon.gif";
servicesoff=new Image();
servicesoff.src= "images/menu/servicesoff.gif";
serviceson=new Image();
serviceson.src= "images/menu/serviceson.gif";
contactoff=new Image();
contactoff.src= "images/menu/contactoff.gif";
contacton=new Image();
contacton.src= "images/menu/contacton.gif";

}

function imageOn (imagename){
  document[imagename].src=eval(imagename+"on.src");
 }
function imageOff (imagename){
  document[imagename].src=eval(imagename+"off.src");
 }