How do servers and browsers treat unknown extensions? (long)

[Amanda Baird <abaird -at- MAIL -dot- OPEN-SOFTECH -dot- COM>]

This may be off topic for this list - but I really need help and I'm having a hard time solidifying this "problem" to a simple query/statement.  Maybe some of you have come across this issue...

 

Here's the question:  I have an application that I want to put online for download.  Then, when you have the app downloaded, you click on a button on a web site, which then launches the app - this application is for use online, so it is always launched off a website.  Now, this app has a new, unknown file extension - no browsers or servers "know" about it (we haven't registered the extension yet).  And, we want to use only one button - you click on the same singular button whether or not you have the program already - if you have it already (you've downloaded & executed the .exe), then a click on the button will launch the application, and if you don't have it, a click on the button will send you to a download page.  The problem, is that the file that the click on the button initiates is a new and unknown file extension - web browsers and servers don't know about it.  So, my question is this: Is there any way to associate a new file extension that is unknown to a web server and a web browser, and have the server redirect the browser to a download page IF the user doesn't have the app already installed, OR if the user DOES have it installed, then launch the application?

 

We can register our new file extension with IANA, but we're trying to avoid that right now...

 

Also, any pointers to where it details how different browsers (IE, Netscape, Apache, etc.)  treat unknown file extensions?

 

Any ideas or suggestions?  Please feel free to reply to me directly, if you think it's inappropriate for the whole list (abaird -at- mail -dot- open-softech -dot- com).

 

Thank you so much!