title: Hide the iframes whose content get blocked by proxy
body: <p>I have a webpage with iframes. 
  These iframes are for showing some external website data.</p>
  
  <p>But problem arise when those external servers get blocked in a network it gives a error that "The proxy server is refusing connections". 
  It does not look good to me. </p>
  
  <p>I want to hide all these blocked iframes or want to show some alternate data there.</p>