title: Chrome extension does not work
body: <p>please do not mark this as duplicate because my question is different. I am trying to make a chrome extension that blocks ads. But it doesn't seem to do anything.
  Here is my code:</p>
  
  <p>manifest.json</p>
  
  <pre><code>{
  "manifest_version": 2,
  
   "name": "Ad Killer",
   "description": "A Basic ad remover",
   "version": "1.0",
  
   "browser_action": {
   "default_icon": "ad128.png",
   "default_popup": "popup.html"
   },
   "permissions": [
     "activeTab",
     "https://ajax.googleapis.com/"
   ]
  }
  </code></pre>
  
  <p>Here is my popup.html:</p>
  
  <pre><code>&lt;html&gt;
  &lt;body&gt;
  
    &lt;script type="text/javascript"&gt;
      var elems = document.getElementsByTagName("iframe"); 
      for(var i = 0, max = elems.length; i &lt; max; i++) {
                   elems[i].hidden=true;
      } 
    &lt;/script&gt;
    &lt;h1&gt; Ads Killed &lt;/h1&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>The problem is that it shows the 'ads killed' message but does not do anything. My question is that is there any way to make it work? I have very little experience in javascript and any help will be very appreciated.</p>