function showDiv( id ) { 
    document.all.Telefoon.style.visibility = 'hidden'; 
    document.all.email.style.visibility = 'hidden'; 
 
    document.all.Telefoon.value            = 'Vul uw telefoonnummer in'; 
    document.all.email.value            = 'geen@mail.be'; 
 
    document.all[ id ].style.visibility     = 'visible'; 
} 

function showTextField(thisField,showField){
        if(thisField.selectedIndex==thisField.options.length-1){
                thisField.form.elements[showField].style.visibility='visible';
                thisField.form.elements[showField].style.color='#FFFFFF';
                thisField.form.elements[showField].value=' Hier invullen a.u.b.';
        }
        else{
                thisField.form.elements[showField].style.visibility='hidden';
                thisField.form.elements[showField].value='';
        }
}