title: find and replace string
body: <p>Is it possible to look at a page's source code, find a certain part and replace it with something else before the page loads? I would like to accomplish this using JavaScript so that I can use it in a Chrome extension. So something like this:</p>
  
  <p>Find the google.com</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  var URLgo = "http://google.com";
  &lt;/script&gt;
  </code></pre>
  
  <p>Replace with yahoo.com</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  var URLgo = "http://yahoo.com";
  &lt;/script&gt;
  </code></pre>