清华大佬耗费三个月吐血整理的几百G的资源，免费分享！....>>>

#emailUs
{
  display: block;
  width: 107px;
  height: 23px;
  background: url("emailUs.gif") no-repeat 0 0;

}

#emailUs:hover
{ 
  background-position: 0 -23px;
}

#emailUs span
{
  position: absolute;
  top: -999em;
}