Wow, my error really was that stupid.
I had the custom.css which I had tried as secondary file in the correct directory, but, really, I hadn't copied the tei.css there, but instead had it, as I said in the post, only in the directory of the xsl...
Now I can move on to find out where I can change the automatic div headings...
> Date: Wed, 20 Nov 2013 11:48:09 +0000
> From: [log in to unmask]
> Subject: Re: TEI->xhtml rend/style questions (other xsl issues in a 2nd post)
> To: [log in to unmask]
> On 20 Nov 2013, at 10:20, Werner Stangl <[log in to unmask]
> > I tried it with a relative path, putting tei.css in the same directory as the xsl files, having in tei-param.xsl
> > <xsl:param name="cssFile" as="xs:string">tei.css</xsl:param>
> > instead of <xsl:param name="cssFile" as="xs:string">http://www.tei-c.org/release/xml/tei/stylesheet/tei.css</xsl:param>
> but the generated HTML is not in the same director as the XSL
> donít forget, the CSS is being read by the browser, and its looking for the URL
> relative to where oxygen writes the HTML. which is generally similar to the input.
> which is why we have a full URL by default, to avoid these issues :-}