a.thumbnail
{
  float: left;
  padding: 10px;
  width: 130px;
  margin: 5px;
  font-size: .9em;
  color: #e1e1e1;
  text-decoration: none;
  border: 1px solid #222222;
  vertical-align: middle;
  text-align: center;
  background: transparent url("../images/transparencias/negro50.png");
  background-repeat: repeat; 
}
a.thumbnail:hover
{
  background: transparent url("../images/transparencias/negro90.png");
  background-repeat: repeat; 
}