var x = new Image(); 
x.src = '/ext/images/menu_bg_onmouse.gif'; 
 
var y = new Image(); 
y.src = '/ext/images/menu_bg.gif'; 
 
 
 
function swapClass(el, class1, class2) { 
if (el.className) 
el.className = (el.className == class1) ? class2 : class1; 
}