Running a specific java version on firefox

I can use the classid "clsid: CAFEEFAC-0015-0000-0011-ABCDEFFEDCBA" to tell it to use Java version 1.5.0_11

No more, you can't, for good (security) reasons. See http://java.sun.com/javase/6/webnotes/deploy/deployment-policy.html

There is an IE-only clsid mechanism that asks for "5.0_ (something)" in general - http://java.sun.com/javase/6/webnotes/family-clsid.html . This was introduced in 5.0u7, so if you have one JRE with u7 and above, you get this behavior, otherwise you get old and incompatible behavior.

Sun did not deign to create a similar mechanism for other browsers prior to 6.0u10, when they added a bunch of more mechanisms for selecting versions and obsolete all the old ones, including the 5.0u7 family of choice. See https://jdk6.dev.java.net/plugin2/version-selection/ for all gory details.

So what behavior you get depends not only on the browser, but also on whether the JVM version is installed, but what other versions are installed. The new behavior is at least consistent, but it is completely different for everyone, which was before and is not completely compatible. By the time the Application Deployment HTML has been updated to handle this, they will probably work with 1.6 anyway.

So, in general, as usual with applets, this is all a bloody mess. Yay.