If you're ever stuck with an older computer and a Live CD (an older version of Knoppix) or an older computer with Windows 95/98/Me and an older version of Firefox or Mozilla or SeaMonkey, then useful extensions (add-ons, but not plugins) for these still exist and can be installed.
(If installing them from a website won't work, download an .xpi separately and install from local storage.)
The most recent version of NoScript to support —
• Mozilla Firefox 1.0.x (in my case): 188.8.131.52 (XPI)NoScript versions page
I know I haven't posted much about Flashblock, but it can be had from flashblock.mozdev.org
The legacy options presented in this post pertain to situations where it's impossible to upgrade to SeaMonkey 1.1.19, such as an out of date Live CD (and what if someone has only that?).
Yet when it comes to a Windows 9x operating system, then it's best to install or upgrade to SeaMonkey 1.1.19. Reasons for this in one of my previous posts.