Javascript - validation, numbers only

Question

I\'m trying to get my login form to only validate if only numbers were inputted. I can it to work if the input is only digits, but when i type any characters after a number,

Answer 1

function ValidateNumberOnly()
{
if ((event.keyCode < 48 || event.keyCode > 57)) 
{
   event.returnValue = false;
}
}

this function will allow only numbers in the textfield.