function validemail(a) {
	if(a=="") {
		return false;
	}
	var exp=/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z]+$/;
	return exp.test(a);
}

function checkall(oForm) {
	var name = ''+document.getElementById('name').value;
	var phonenumber = ''+document.getElementById('phonenumber').value;
	var email = ''+document.getElementById('email').value;
	
	if (name == '') {
		alert("Please enter your name")
		return false;
	} else if (phonenumber == '') {
		alert("Please enter your phone number")
		return false;
	} else if (!validemail(email)) {
		alert("Please enter a valid email address")
		return false;
	} else {
		oForm.submit();
	}
}