var preload_image_object = new Image();
var list = $$('.menuButtons img');	
list.each(function(element) {			
	if(element.attributes['src'].value.indexOf('-off') > 0){
		preload_image_object.src = element.attributes['src'].value.replace("-off","-hover");   												
		element.addEvent('mouseenter', function(){ 
			this.src = this.src.replace("-off","-hover");

		});
		element.addEvent('mouseleave', function(){ 
					this.src = this.src.replace("-hover","-off");
		});	
	}
});