function isNotEmpty(elem) {
    var str = elem.value;
    if(str == null || str.length == 0) {
        alert("Please fill in the required field.");
        return false;
    } else {
        return true;
    }
}

function validateForm(form) {

            if (isNotEmpty(form.email)) {
return true;
    }
    return false;
}