title: Find out if someone is logged in gmail, yahoo and facebook
body: <p>I am working on a web application where I have to tell user that he is logged in <code>gmail</code> or <code>yahoo</code> or <code>facebook</code> account. I think this can be done using <code>cookies</code>. 
  <br/>
  How to find out it? 
  <br/>what is the cookie name of these accounts, so that I can check their presence</p>