function only_numbers() {
	var isNS4 = (navigator.appName=="Netscape")?1:0;
	
	if (!isNS4) {
		if (event.keyCode < 45 || event.keyCode > 57) event.returnValue = false;
	}
	else {
		if (event.which < 45 || event.which > 57) return false;
	}
}