//preload images
   buttones=new Array();
   buttones_over=new Array();

   for(i=0;i<8;i++){
       buttones[i]=new Image();
       buttones_over[i]=new Image();}

   imagepath="images/left_nav/";

   buttones[0].src=imagepath + "students.gif";
   buttones_over[0].src=imagepath + "students_over.gif";

   buttones[1].src=imagepath + "faculty.gif";
   buttones_over[1].src=imagepath + "faculty_over.gif";

   buttones[2].src=imagepath + "campus.gif";
   buttones_over[2].src=imagepath + "campus_over.gif";

   buttones[3].src=imagepath + "quick_facts.gif";
   buttones_over[3].src=imagepath + "quick_facts_over.gif";

    for(i=4;i<8;i++){
      buttones[i].src="images/bottom_img/button.gif";
      buttones_over[i].src="images/bottom_img/button_over.gif";}

//menu functions

   function over(item) {
         document.getElementById("btn_img_"+item).src=buttones_over[item].src;
   }
   function out(item) {
         document.getElementById("btn_img_"+item).src=buttones[item].src;
   }