.tweet-button div {
	float: left;
	width: 55px;
	height: 20px;
	background: url('/sites/all/modules/custom/ptsocialwidgets/tweet-button.gif') top left no-repeat;
	margin: 0 10px; 
}
.tweet-button:hover div {
  background: url('/sites/all/modules/custom/ptsocialwidgets/tweet-button.gif') bottom left no-repeat; 
}