title: How to create WiFi popup login page
body: <p>When I go to a place with a WiFi hotspot (such as Panera Bread) and connect with my iPhone, the hotspot login page appears as a popup. That is, no matter what app I'm running or what web page I'm on, the login page scrolls up from the bottom, asks for my login credentials, and then disappears.</p>
  
  <p>But at some other hotspots, I don't get the login page until I go to Safari and try to load a web page.</p>
  
  <p>What is the iPhone looking for that causes it to pop up the login page at some hotspots and not others? Is there a special HTML meta tag? Or is it related to the way the redirect is implemented?</p>