title: Allow only certain domains being able to load an iFrame
body: <p>I'm building some widgets for a charity. Due to some logo licensing malarkey, I've got to find some way of only allowing white-listed sites from running the code, or to send a error message (or something like that) rather than the widget.</p>
  
  <p>We've got to use iFrames as a fair few sites have already embedded them.
  Ideally, a PHP solution would be best, but JS is ok if needs be.</p>
  
  <p><strong><em>So, the one liner; Can I check the domain the iFrame is sitting in and send it different content?</em></strong></p>
  
  <p>I wonder what the chances are of being able to do this...</p>