title: Chrome extension, reading a content of HTML element
body: <p>I am trying to develop an extension for Chrome browser. I know what I want to achieve, but there are many ways to achieve it, some are more complicated than others.</p>
  
  <p>I wish to parse the content of the currently viewed email, do some processing on it, than replace the original content with the modified one. I want to use the extension on famous email clients, such as Gmail, Yahoo, Hotmail, etc.</p>
  
  <p>Apparently, it is hard to recognize which part of the HTML holds the content of the email. I assume that if the identifier (or class) of the HTML element, which holds the content, is known, then it should be straightforward to retrieve the content, process it, and inject it back.</p>
  
  <p>Any clue what is the best method to do so? Any references, and snipped codes will be great.
  <strong>Remember, simplicity is a bliss :)</strong></p>
  
  <p>Thanks.</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>To clear any doubts, I am not trying to do anything malicious. I wish to implement a specific-proofing tool for my academic thesis.</p>