window.onload = function() {
	initRollover();
}

function initRollover() {
    var count= 0;
    var images = document.getElementsByTagName("img");
    
    for (var i = 0; i <images.length; i++) {
       if(images[i].className == "rollover") {
	   
		   var rolloverImage = images[i];
			
			rolloverImage.onmouseover = function(){
				this.src = "images/"+this.id+"_on.gif";
				}
				
			rolloverImage.onmouseout = function() {
				this.src = "images/"+this.id+"_off.gif";
				}
	   }
	}
}