ul.ex_button { 
width:463px;
margin:15px 0 30px 117px;
padding:0;
 }
ul.ex_button li {
 float: left;
 margin: 0 4px 4px 0;
}
ul.ex_button li img {
 border:0;
 width:150px;
 height:100px;
}
ul.ex_button li a {
display: block;
}
ul.ex_button li a:hover img{
-moz-opacity:0.5;
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
filter: Alpha(Opacity=50);
opacity: .5;
}