As far as I know, there's nothing to tailor. The browser either recognizes the ".jnlp" extension and/or the "application/x-java-jnlp-file" MIME type or it doesn't, depending on whether it has an appropriate Java plugin installed.
I'm far from experienced when it comes to Java Web Start, though, so I might easily be wrong about things.
Lasse, you are not wrong. We are using Java Web Start extensively, and I'm quite sure that we don't have browser-specific jnlp-files.
The reason is simple: the only thing the browser has to do is to pass the jnlp-file to the Web Start launch application. After that, it's out of the loop. (Please somebody correct me if I'm wrong.)
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
Everyone is right! Except for one small statement Lasse made:
depending on whether it has an appropriate Java plugin installed.
Launching a web startable app doesn't depend on the browser having the plugin installed. The server just has to recognize the MIME type, as Lasse stated, and that information is passed back to the client. The client will need to have JWS installed which has been a default thing since 1.4. I believe with 1.3 it was an optional installs.
The application still relies on the security sandbox model that applets do, however, they are much more flexible and easier to manage. I think JWS is an awesome technology and a great way to distribute applications. [ August 31, 2006: Message edited by: Gregg Bolinger ]