iframe-addressbar.user.js

// ==UserScript==
// @name           iframe-addressbar
// @namespace      http://d.hatena.ne.jp/edvakf/
// @description    Show pseudo address-bars for iframes on load and mouseover
// @include        *
// ==/UserScript==

(function(win) {
  if (win.top === win.self) return;

  var initial_opacity = 0.8;
  var isShown = false;
  function showPseudoAddressBar() {
    if (isShown) return;
    isShown = true;
    with (location) {
      var origin = protocol + '//' + host + (port ? ':' + port : '');
    }
    var bar = document.createElement('p');
    bar.textContent = origin;
    bar.setAttribute('style',
      ['background-color : black'
      ,'color : white'
      ,'border : solid white 1px'
      ,'margin : 0'
      ,'padding : 0'
      ,'opacity : ' + initial_opacity
      ,'position : fixed'
      ,'z-index : 65535'
      ,'top : 0'
      ,'left : 0'
      ].join(';')
    );

    document.body.appendChild(bar);
    setTimeout(function() {
      var duration = 500; // millisecond
      var t = new Date;
      var timer = setInterval(function() {
        var fraction = (new Date - t) / duration;
        bar.style.opacity = initial_opacity * (1 - fraction);
        if (fraction >= 1) {
          bar.parentNode.removeChild(bar);
          clearTimeout(timer);
          isShown = false;
        }
      }, 50);
    }, 2500);
  }

  win.addEventListener('load', showPseudoAddressBar, false);
  win.addEventListener('focus', showPseudoAddressBar, false);

}(this.unsafeWindow || this));