$(function(){     $("img.rollover").mouseover(function(){         $(this).attr("src",$(this).attr("src").replace(/^(.+)(\.[a-z]+)$/, "$1_on$2"))     }).mouseout(function(){         $(this).attr("src",$(this).attr("src").replace(/^(.+)_on(\.[a-z]+)$/, "$1$2"));     }).each(function(){         $("<img>").attr("src",$(this).attr("src").replace(/^(.+)(\.[a-z]+)$/, "$1_on$2"))     }) })