The fact that you are reading this page shows that Privoxy was not used in the process of accessing it. Had the request been made through Privoxy, it would have been intercepted and you would be looking at Privoxy's web-based user interface now.
So what went wrong? Chances are (in this order) that:
this page is in your browser's cache. You've once been here before starting to use Privoxy, and now your browser thinks that it already knows the content of this page. Hence it doesn't request a fresh copy.
Force your browser to do that. With most browsers, clicking "reload" while holding down the shift key (shift-reloading) should suffice, but you might need to manually clear the browser's cache (both memory and disk cache).
your browser is not set up to use Privoxy.
Check your browser's proxy settings and make sure that it uses 127.0.0.1, port 8118 (or, if you did a custom configuration, whatever different values you used).
when using multiple proxies in a chain, that either the chain is broken at some point before Privoxy, or that an earlier proxy serves this page from its cache.
Shift-reload, clear all caches, and if the problem still persists, trace the proxy chain starting with your browser's settings. Please refer to the forwarding chapter of the user manual for details.
Until version 2.9.13, Privoxy was also known as Internet Junkbuster. If you recently upgraded, then the web-based interface has moved - it is now at http://config.privoxy.org/ (Short form: p.p [Privoxy Proxy]).
If you have read the user manual and still have trouble, feel free to submit a support request to get help.