title: How does Stack Overflow notify of server-side events without a page reload? I see no request in Firebug
body: <p>How does Stack Overflow show the answer added/edited message without a page reload?</p>
  
  <p><img src="https://i.stack.imgur.com/XJ5Wx.jpg" alt="enter image description here"></p>
  
  <p>Yes, I know it will happen with Ajax. So I opened Firebug in a browser to check it, to see whether any requests are coming in a particular interval of time.
  But I don't see any request coming in Firebug. </p>
  
  <p>Can we perform a request without it showing in Firebug?
  Are there any other ideas behind this or is my concept totally wrong?</p>