function roll_on() {
			  this.src = this.src.replace(/_off/,'_on');
			}
			
			function roll_off() {
			  this.src = this.src.replace(/_on/,'_off');
			}
			 
			function img_roll() {
				var listimg = document.getElementById('headerBottom').getElementsByTagName('img');
			  for (i = 0; i < listimg.length; i++) {
			
				if (listimg[i].src.indexOf('_off.') > 0) {
			
				  listimg[i].onmouseover = roll_on;
			
				  listimg[i].onmouseout = roll_off;
				}       
			  }
			}
			
			setTimeout("img_roll();",800);