function formHandler(form){
	var isValid = true;
	if (document.form.zip.value.length < 5) {
		
		isValid = true;
	}
	else if (isNaN(document.form.zip.value)) {
		
		isValid = true;
	}
		
	if (isValid) {
		var URL = document.form.site.options[document.form.site.selectedIndex].value;
		URL = URL + "&zip=" + document.form.zip.value;
		window.location.href = URL;
	}
}