function checkFields(){

    if (document.forms.tellAFriend.sName.value == '') {
        alert('Please specify your name');
        return
    }


    if (document.forms.tellAFriend.sEmail.value == '') {
        alert('You have to specify your e-mail address');
        return
    }

    if (document.forms.tellAFriend.sSendersEmail.value == '') {
        alert('You have to specify your e-mail address');
        return
    }

    document.forms.tellAFriend.submit();

}