While you can run GI 3.9 on Firefox 4, you must get pass the browser support warning dialog. As far as we can tell, there is no compatibility issue for GI 3.9 and Firefox 4. So, you can get pass this warning dialog by adding a deployment parameter
jsx_browsers. Overrides the default set of supported browsers. The format of this parameter is
where bt is the browser type returned by the getType() method in the jsx3.lang.ClassLoader class. See jsx3.lang.ClassLoader in General Interface API Reference.
allow launches the application in the browser.
warn provides a warning for unsupported browsers and allows the user to proceed
For example, to show a warning in Internet Explorer 6 and allow Firefox 4, modify the application launch page as follows:
The next version of GI should have Firefox 4 support enabled by default, so you will not need to do this. However, if you can't wait this is how you do it.