.viewer {  
margin: 0 auto;  
width: 950px;  
height: 300px;  
text-align: left;  
overflow: hidden;  
 }  

.viewer ul {  
width: 950px;  
height: 300px;  
text-align: left;  
overflow: hidden;  
position: relative;  
 }  

.viewer ul li {  
top: 0;  
left: 0;  
width: 950px;  
height: 300px;  
display: none;  
position: absolute;  
 }