function isValidEmail(email)
{
    var re = /^\w[\w\.]*@[\w]+(\.[\w]+)*$/i;
    return re.test(email) ? true : false;
}

function validateEmail(where)
{
    if (false == isValidEmail(where.value)) {
        alert('The email is incorrect!');
        where.focus();
        return false;
    }
    return true;
}