var IE =  !!(window.attachEvent && navigator.userAgent.indexOf('Opera') === -1);

function acceptNum(evt){
	// NOTE: Backspace = 8, Enter = 13, '0' = 48, '9' = 57
	var key = IE ? evt.keyCode : evt.which ;
	return (key <= 32 || key <= 13 || (key >= 48 && key <= 57));
}

function acceptNumLetters(evt){
	var key = IE ? evt.keyCode : evt.which ;
	return (key <= 13 || (key >= 48 && key <= 57) || (key >= 65 && key <= 90) || (key >= 97 && key <= 122)  || (key == 32));
}