var myrules = {
	'#menu-left img' : function(element){
		element.onmouseover = function() {
			var overSrc = this.src.replace('.gif', '_hover.gif');
			this.src = new Image().src = overSrc;
			
		},
		element.onmouseout = function() {
			var overSrc = this.src.replace('_hover', '');
			this.src = new Image().src = overSrc;
		}
	}
};

Behaviour.register(myrules);