#button{
    width: 12em;
    border-right: 1px solid #000;
    padding: 0 0 1em 0;
    margin-bottom: 1em;
    font-family: 'Trebuchet MS', 'Lucida Grande',
      Verdana, Lucida, Geneva, Helvetica,
      Arial, sans-serif;
      background-color: #666666;
      color: #333;
      }
#button ul {
           list-style: none;
           margin: 0;
           padding: 0;
           border: none;
           }  
 #button li{
border-bottom: 1px solid blue;
margin: 0;
}
#button li a{
             display: block;
             padding: 5px 5px 5px 0.5em;
             border-left: 10px solid blue;
             border-right: 10px solid blue;
             background-color: silver;
             color: #fff;
             text-decoration: none;
             width: 100%;
            }
html>body #button li a {
     width: auto;
     }

#button li a:hover {
    border-left: 10px solid blue;
    border-right: 10px solid blue;
    background-color: green;
    color: #fff;
}