Greasemonkey script which detect patterns in html source.

detect-patterns.user.js

// ==UserScript==
// @name           detect-patterns
// @namespace      anbt
// @include        *
// ==/UserScript==

(function(){
   if (window != unsafeWindow.top) { return; }


   var patterns = [
     "vevent"
     , "vcalendar"
     , "rel='license'"
     , 'rel="license"'
     , "hreview"
     , "hentry"
     , "creativecommons.org"
     , "commons"
     , "http://ogp.me/ns#"
   ];


   var doc = document;


   function createElement(parent, tagName, attributes, styles, innerHTML){
     var e = doc.createElement(tagName);

     if(attributes){
       for(var key in attributes){
         e.setAttribute(key, attributes[key]); }}
     if(styles){
       for(var key in styles){
         e.style[key] = styles[key]; }}
     if(innerHTML){
       e.innerHTML = innerHTML; }
     if(parent){
       parent.appendChild(e); }

     return e;
   }


   // javascript - How do I do OuterHTML in firefox? - Stack Overflow
   // http://stackoverflow.com/questions/1700870/how-do-i-do-outerhtml-in-firefox
   function outerHTML(n){
     var div = doc.createElement('div'), h;
     div.appendChild( n.cloneNode(true) );
     h = div.innerHTML;
     div = null;
     return h;
   }


   ////////////////////////////////
   // Main

   function detect(target, pattern){
     if( ! target.match(pattern) ){
       return;
     }
     
     createElement(
       container
       , "p"
       , {}
       , { background: "#c00"
           , color: "#fff"
           , padding: "1ex"
           , margin: "1ex"
           , zIndex: "1000"
           , fontWeight: "bold"
         }
       , pattern.toString()
     );
   }


   var container = createElement(
     doc.body
     , "div"
     , {}
     , { position: "fixed"
         , right: "0", top: "0"
         , color: "#fff"
         , padding: "0"
         , zIndex: "1000"
         , background: "#fff"
         , opacity: "0.8"
       }
   );

   container.addEventListener(
     "click"
     , function(e){
       e.target.style.display = "none"; 
     }
     , false
   );


   var html = doc.getElementsByTagName("html")[0];
   var target = outerHTML(html);

   for(var a=0, len=patterns.length; a<len; a++){
     detect(target, patterns[a]);
   }
 })();