Currently you can't access any methods which a Nav4 plugin may have which effectivly breaks a lot of pages. The ones that come to mind would be ones that use the Flash fs command. And the ones we are currently developing at work (To be released in a couple weeks).
We've been over this issue many times, so I'm virtually certain this is a WONTFIX because of the enormous difficulty of the task, but it's not my decision to make. Due to the design of the old NN system for plugin methods, which required the active cooperation of the JVM, any attempt at implementing this functionality could only be partially effective. If anyone is interested in taking up this task, however, I can outline the broad steps necessary to write the adapter code. Anyway, passing this bug on to the owner of plugins.
Changing to REMIND
reopening and marking future
reopening and marking future...
Let's stop kidding ourselves. This is infeasible for technical reasons due to the dependency on the now-defunct Nav4 JVM and the fact that we'd need to get third-party JVMs hacked in baroque ways to try to fix this. The way this problem will actually be solved is for plug-in vendors to upgrade their plug-ins to support the Mozilla Plug-in API, not through hacking both Gecko and multiple third-party JVMs to try to emulate the old calls. (Major plug-in vendors will have finished their upgrades long before any such hackery would be completed, and as fur notes it would likely be only partially successful at best anyway.) Marking WONTFIX. Netscape definitely won't be supplying engineering resources to attempt to fix this. If anyone chooses to reopen, they should reassign both eng and qa contacts to firstname.lastname@example.org (or themselves) and mark helpwanted. But again, I think that would be people kidding themselves, and I think that the nglayout module owners would be reluctant to take a half-working fix into the codebase.