pre {
  font-size: x-large;
  width: 38em;                      /* 60 chars approx */
  background-color: cornsilk;  
  /* colors: lemonchiffon, ivory, honeydew, floralwhite, cornsilk
   */
  border: 2px solid black;
  padding-top: 0.2em;
  padding-left: 0.5em;              
  padding-right: 0.5em;             
  counter-reset: line;
}
pre span:before {
  counter-increment: line;
  content: counter(line);
  display: inline-block;
  border-right: 1px solid #ddd;
  padding: 0 .5em;
  margin-right: .5em;
  color: #888
}