function is_loaded() { //DOM
if (document.getElementById){
document.getElementById('preloader').style.visibility='hidden';
document.getElementById('contenedor').style.visibility='visible';

}else{
if (document.layers){ //NS4

document.preloader.visibility = 'hidden';
document.contenedor.visibility = 'visible';

}
else { //IE4

document.all.preloader.style.visibility = 'hidden';
document.all.contenedor.style.visibility = 'visible';
}
}
}