function makevisible(){
box = document.getElementById('hidden');
box.style.display = 'block';
box.style.visibility = 'visible';
}
howmanyseconds = 1500;
setTimeout('makevisible()', howmanyseconds*1000);

function clearText(field){
if (field.defaultValue == field.value) field.value = '';
else if (field.value == '') field.value = field.defaultValue;
}