Steven Chan posted on his blog yeterday that Oracle has announced certification of E-Business Suite and Firefox 3. There are some pre-requisites which should be carefully reviewed, but this is great news for E-Business Suite customers pining to get off of Firefox 2.
The framework patch 7651759 in particular specifically targets Firefox 3 users and includes a number of Firefox 3-specific fixes.
With regards to your plug-in type: “If using next-generation JRE plug-in technology (JRE 1.6.0_10 and later) we strongly recommend that you apply patch 7567782 which removes the use of the jpi-parameter and switches Firefox to a non-static versioning model.”