.shell
{
  color: #000; 
  margin-left: auto;
  margin-right: auto;
  width: 648 px; 
}

.shell p
{
  margin: 1em; 
}

.shell table
{
  width: 648px;  
  border:1px solid #000; 
  text-align:center; 
}

.shell th
{
   text-align:center;
   border-bottom: 1px solid #000; 
}