CodeHighlighter.addStyle("xml", {
  comment : {
    exp: /<!\s*(--([^-]|[\r\n]|-[^-])*--\s*)>/
  },
  tag : {
    exp: /(<\/?)([a-zA-Z]+\s?)/, 
    replacement: "$1<span class=\"$0\">$2</span>"
  },
  attribute : {
    exp: /\b([a-zA-Z-:]+)(=)/, 
    replacement: "<span class=\"$0\">$1</span>$2"
  },
  doctype : {
    exp: /&lt;\?xml.*&gt;/
  }
});