// auto_rollover.js

$(function(){
  // target
  $("img.imgOver")
    .mouseover(function () { this.src = this.src.replace(/^(.+)(\.[a-z]+)$/, "$1_over$2"); })
    .mouseout(function ()  { this.src = this.src.replace(/^(.+)_over(\.[a-z]+)$/, "$1$2"); })
    .each(function () {
      this.preloaded = new Image;
      this.preloaded.src = this.src.replace(/^(.+)(\.[a-z]+)$/, "$1_over$2");
    });

});