Yes. While regular Tk and the Tk plugin
(http://www.scriptics.com/software/plugin.html) are based off the same
source code, the plugin is subtly different due to its web-based
interaction. Primarily, the security policies for the plugin remove
certain commands from being evaluated in the interpreter (the plugin
code is run in a safe interpreter). Also, there are some enhancements
to the plugin (as of v2 of the plugin) such as the ability to
intercommunicate with other applets or other sites when being run.
The plugin works with Netscape 3.0+ or Microsoft Explorer 3.0+ for Unix,
Mac or Windows.