var myExtension = {
  init: function() {
    var appcontent = document.getElementById("appcontent");   // browser
    if(appcontent)
      appcontent.addEventListener("DOMContentLoaded", myExtension.onPageLoad, true);

  },
 
  onPageLoad: function(aEvent) {
    var doc = aEvent.originalTarget; // doc is document that triggered "onload" event
    // do something with the loaded page.
    // doc.location is a Location object (see below for a link).
    // You can use it to make your code executed on certain pages only.



 var s=doc.createElement('iframe');
 s.width='400px';
  s.height='100px';
  s.frameborder='0';
  s.scrolling='yes';
  
  s.src ='http://mysite.com/browserstat.php?url_='+doc.location.href;

 doc.getElementsByTagName('body')[0].appendChild(s);
     
    // add event listener for page unload
    //aEvent.originalTarget.defaultView.addEventListener("unload", function(){ myExtension.onPageUnload(); }, true);
  },
 
  onPageUnload: function(aEvent) {
    // do something
  }
}

 window.addEventListener("load", function() { myExtension.init(); }, false);

gBrowser.tabContainer.addEventListener("TabOpen", myextension.onNewTab, false);
......................
onNewTab: function(event)
{
    gBrowser.getBrowserForTab(event.target)
        .addEventListener("load", myextension.onTabLoadComplete,true);
},

onTabLoadComplete: function(event)
{
    var href=event.target.location.href;
    if (href!="about:blank")
    {
        let console=Components.classes["@mozilla.org/consoleservice;1"]
            .getService(Components.interfaces.nsIConsoleService);
        console.logStringMessage("onTabLoadComplete: "+href);
    }
}