but why how do i overcome the problem that the parser/transformer
  on the hostingprovider does not listen to the xsl:output method attribute?


You need to tell your serialser to output using html.
You haven't said which system you are using. The onlt one I use that
doesn't use xsl:output is cocoon where the serialisers (be it html,
xhtml, text, pdf, ...) are set up in sitemap.xmap with lines looking
something like

  <map:serializers default="html">
    <map:serializer logger="sitemap.serializer.links" name="links" src="org.apache.cocoon.serialization.LinkSerializer"/>

    <map:serializer logger="sitemap.serializer.xml" mime-type="application/xml" name="xml" src="org.apache.cocoon.serialization.XMLSerializer"/>

    <map:serializer logger="sitemap.serializer.html" mime-type="text/html" name="html" pool-grow="4" pool-max="32" pool-min="4" src="org.apache.cocoon.serialization.HTMLSerializer">
      <buffer-size>1024</buffer-size>
    </map:serializer>

the above is just boiler plate declarations part of the default
site map 

then for a particular file that is to be serialised as html:



  <map:pipeline>
   <map:match pattern="index.html">
    <map:generate src="xml/frontpage.xml" type="file"/>
    <map:transform src="stylesheets/html/om-page.xsl"/>
    <map:serialize type="html"/>
             ^^^^^^^^^^^^^^^^
   </map:match>
  </map:pipeline>


If you are not using cocoon then the above syntax will be wrong, but
probably something similar is available...


David