When your Javascript is not working in browser (IE or FF or Chrome latest version), you can replace the codes  window.location.href (or) document.location.href with the one below. Somehow, setTimeOut works across all browsers with latest version (IE 8 &9, FF 8.0.x, Chrome 23.0.1271.x

function redirect_home(){
setTimeout(function(){document.location.href = "ext_search.php?mode=dropoff"},500);
}