function checkEmail()
{

    var email = document.getElementById("email").value;
    var strReg = "^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$";
    var regex = new RegExp(strReg);
    if(regex.test(email) == true)
    {
        return true;
    }
    else
    {
        alert("Bitte gültige Email Adresse eingeben!");
        return false;
    }
}
function clearEmail()
{
    if(document.getElementById("email").value == "Email-Adresse")
        document.getElementById("email").value = "";
}