while (enumerator.hasMoreElements()) 
{
    v_window = enumerator.getNext();
    v_browser = v_window.getBrowser().browsers;
    for (var i = 0; i < v_browser.length; i++)
    {
        v_tab = v_browser [i];
if (v_tab.contentDocument.baseURI.indexOf("blablablabla")!=-1){        
        v_doc = v_tab.contentDocument;
        var docEl = v_doc.defaultView.document.documentElement;
        var tagWindow=v_window;
        tagWindow.document.addEventListener("DOMSubtreeModified",LoadSite, false);
      
     } 

    }
}
        if (v_doc==null) {alert("Не попали!");} else {alert("Попали!");}

function LoadSite (ev)
{
if (v_doc!=null){
  netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
  netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserRead');

iframe=temp[2].contentDocument.getElementById("iframe_name");
iframe.contentWindow.document.addEventListener("load",btl, true);
temp=iframe.contentWindow.document.getElementsByTagName('SCRIPT')[0].innerHTML;
                   }
}

function btl()
{
  alert("Загрузилось");
}