gBrowser.tabContainer.addEventListener("TabAttrModified", function(e) { 
   var tab = e.target;
   if ( tab.linkedBrowser.contentDocument.domain !== 'ru.savefrom.net' ) return;
   gBrowser.selectedTab = tab;              
   
   this.removeEventListener(e.type, arguments.callee, true);
}, true );

loadURI ("javascript:(function(){ window.open('http://savefrom.net/?url=' + escape(location.href)) })()");