I have a 64-bit Ubuntu. For the preinstalled Firefox I had to download the 64-bit plugins (Flash, Java); the 32 bit plugins didn't work. Then I downloaded Firefox from mozilla.org, which just has one version to download, and it does not state whether it is 32 bit or 64 bit (as of november 2010). Using this downloaded Firefox all the 64-bit plugins no longer work. I had to download the 32 bit plugins.
How can I tell whether my Firefox is 32 bit or 64 bit?