ul.thumb {float: left;list-style: none;margin: 0; padding: 20px; width: 900px; margin-top: 0px; background-color: transparent;}
ul.thumb li {margin: 0; padding: 10px;float: left;position: relative;width: 150px;height: 150px;}
ul.thumb li img {width: 140px; height: 140px; border: 3px solid #494949; padding: 7px;background: #000; position: absolute;left: 0; top: 0; }
ul.thumb li img.hover {margin-top:15px;background:url(thumb_bg.png) no-repeat center center;border: none;}