MediaWiki:Monobook.css

/* CSS placed here will affect users of the Monobook skin */
div.mw-geshi {
  padding: 1em; 
  margin: 1em; 
  border: 1px dashed #2f6fab;
  background-color: #f9f9f9;
}

pre {
  padding: 1em;
  margin: 1em;
  font-size: 1em;
}