December 16, 2008
Java Plugin for Windows x64
Sun released Java plugin for Windows x64. So you can use Java applet on Firefox x64.
You can download it from Javaâ„¢ Platform, Standard Edition 6u12 Binary Snapshot Releases. This JDK release has 64-bit plugin.
Reference: Bug ID: 4802695: Support 64-bit Java Plug-in and Java webstart on Windows/Linux on AMD64