var myimages=new Array()
function preloadimages(){
for (i=0;i<preloadimages.arguments.length;i++){
myimages[i]=new Image()
myimages[i].src=preloadimages.arguments[i]
}
}

preloadimages('images/btn-home-on.jpg', 'images/btn-home.jpg',
              'images/btn-publication-on.jpg', 'images/btn-publication.jpg',
              'images/btn-research-on.jpg', 'images/btn-research.jpg',
              'images/btn-teaching-on.jpg', 'images/btn-teaching.jpg');