if (document.images) {
galleryoff=new Image();
galleryoff.src= "images/galleryoff.jpg";
galleryon=new Image();
galleryon.src= "images/galleryon.jpg";
aboutoff=new Image();
aboutoff.src= "images/aboutoff.jpg";
abouton=new Image();
abouton.src= "images/abouton.jpg";
contactoff=new Image();
contactoff.src= "images/contactoff.jpg";
contacton=new Image();
contacton.src= "images/contacton.jpg";

}

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