function validate(f){
    if (f.txtNumber.value == "") {
        alert("Please enter the number of people in your party.")
        f.txtNumber.focus()
        return false;
    }
    if (f.txtFirstName.value == "") {
        alert("Please enter your first name.")
        f.txtFirstName.focus()
        return false;
    }
    if (f.txtLastName.value == "") {
        alert("Please enter your last name.")
        f.txtLastName.focus()
        return false;
    }
    if ((f.txtEmail.value == "") && (f.txtTel.value == "")) {
        alert("Please enter your email address and / or your telephone number.")
        f.txtEmail.focus()
        return false;
    }
    return true;
}