$(document).ready(function(){

	var preImage = new Array();

  $("img.ro").each(function(i){

    preImage[i] = new Image();

    preImage[i].src = $(this);

  });

	$("img.ro").each(function() {

  	var preImage = new Array();

		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; });

	});

});