First of all I have changed my thickbox.php in this line as the information for height a.s.o was not correct displayed !
Now it works fine.
$output = '<a href="'.$page.'?height='.$height.'&width='.$width.'&modal='.$modal.'" class="'.$embedtype.'" title="'.$title.'">'.$buttontxt.'</a>';
OK I have created a new document [with doc ID 57] and without any css !
Than I put the following call into my test document:
[!ThickBox? &embedtype=`thickbox` &title=`Please Sign In` &page=`[~57~]` &height=`85` &width=`250` &modal=`true` &buttontxt=`Login`!]
but all that I get is a empty box ! In Firebug I can see the following output:
<div id="TB_overlay" class="TB_overlayBG"/>
<div id="TB_window" style="margin-left: -140px; width: 280px; margin-top: -220px; display: block;">
<div id="TB_ajaxContent" class="TB_modal" style="width: 250px; height: 395px;"/>
</div>
It seems that the document is not submitted to ThickBox !