Configuration changes I prefer to make on MediaWiki installations:

<kbd>

1. edit includes/Sanitizer.php (/usr/share/mediawiki/includes/Sanitizer.php in the default Ubuntu install)
   • add 'kbd' => $common to "$whitelist = array ("
   • add 'kbd' to "$htmlpairs = array_merge("
2. restart Apache
3. login to an admin account on the wiki
4. edit MediaWiki:Common.css, and add:
   kbd {background-color:#bbb}