var pics;
  pics = new Array();
// -->
<!-- hide
var objCount = 0;
function preload(name, first, second) {  
    pics[objCount] = new Array(3);
    pics[objCount][0] = new Image();
    pics[objCount][0].src = first;
    pics[objCount][1] = new Image();
    pics[objCount][1].src = second;
    pics[objCount][2] = name;
    objCount++;
}
function on(name){
     for (i = 0; i < objCount; i++) {
      if (document.images[pics[i][2]] != null)
        if (name != pics[i][2]) { 
        document.images[pics[i][2]].src = pics[i][0].src;
        } else {
          document.images[pics[i][2]].src = pics[i][1].src;
        }
    }
}
function off(){
     for (i = 0; i < objCount; i++) {
      if (document.images[pics[i][2]] != null) 
       document.images[pics[i][2]].src = pics[i][0].src;
    }
}
// preload images
preload("button1", "images/school_calendar_red.gif", "images/school_calendar_red_off.gif");
preload("button2", "images/photo_Gallery_towel.gif", "images/photo_Gallery_towel_off.gif");