幻灯片叠加菜单

Question

问题链接：http://comingsoonnurul.blogspot.com/ 为什么幻灯片叠加菜单？

HTML：

<div id="cf4a" class="shadow" >
  <img= src="http://css3.bradshawenterprises.com/images/Windows%20Logo.jpg">
  <img src="http://css3.bradshawenterprises.com/images/Turtle.jpg">
  <img src="http://css3.bradshawenterprises.com/images/Rainbow%20Worm.jpg">
  <img src="http://css3.bradshawenterprises.com/images/Birdman.jpg">
</div>

的CSS：

#cf4a {
  position:absolute;
}

#cf4a img {
  position:absolute;
   height:105px;
  width:200px;
 left:0;
}