5
It's not the css, i think. check the source (head and body tags) when in quirksmode:
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="nl" lang="nl"><head>head><body id="extcal" class="nl">
<meta http-equiv="content-language" content="nl">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>etc.....
I think it has somtething to do with how xoops themes stuff.
In the screenshot's case adding
$xoopsOption['template_main'] = '';
to extcal/comment_new.php avoids quirksmode.
Thats how i did it at other modules, but its just a workaround, i think.