$(document).ready(function(){
	$("img.ro").each(function() {
		var off = this.src;
		var dot = this.src.lastIndexOf('.');
		var on = this.src.substr(0, dot) + '_over' + this.src.substr(dot, 4);
		$(this).hover(function() { this.src = on; }, function() { this.src = off; });
	});
});