Here is the solution to my questions in postings 91060 and 91067: To get Java Web Start working with Zope, I used the Zope product "ExternalFile". Therefore I could integrate the jnlp-file with the correct mime type that is "application/x-java-jnlp-files". This is not included in the ExternalFile product but it is simple to append it in file mime.types of the product. Further description by Craeg K Strong: Look at http://www.zope.org/Members/arielpartners/ExternalFile/readme So if you installed Zope at c:\zope Then you would look for the file c:\zope\lib\python\Products\ExternalFile\etc\mime.types And add the line application/x-java-jnlp-file jnlp # Java webstart files to it. Then you restart Zope (or just refresh the ExternalFile product) And you're done!