title: StackOverflow: Automatic information about update
body: <p>On any page of SO, the page automatically tells me if there is any update. That is, the page automatically displays the info "There is one question with update" or so.</p>
  
  <p>I was curious how this is implemented. I opened my chrome browser, opened the developer tools, "Network" tag, but cannot see any request sending to the server, although there appears the info about a new question with update. </p>
  
  <p>What is the technique to achieve this kind of behavior? Server push? Web socket? Does not the developer tools in browsers display such activities?</p>
  
  <p><strong>EDIT</strong> Moreover, when I click on the info "one question with update", then the new question is displayed, but in the developer tools I don't even see the question (text) being transferred. What I see is only that an icon (PNG) is retrieved from the server, which is the icon of the user asking that question. So, how is the question transferred?</p>