GlimmerBlocker is no longer maintained and should no longer be used as web sites have migrated from using plain http to using https (i.e. encrypted) which prohibits modification by a proxy unless you resort to install custom SSL certiticates on the client.
You should use a browser extension instead.
It was made as a hobby project during 2007-2008 by Peter Speck. It features both a custom http server and http client and a Mac OS X control panel.
Use the latest version available from the homepage.
GlimmerBlocker-1.6.5.dmg (release notes).
GlimmerBlocker-1.5.3.dmg (release notes). When installing GlimmerBlocker, you might be prompted to install Java. Some users need to re-run the GlimmerBlocker installer after the java installer is done.
Parental controls: There is a bug in Lion's parental controls, which breaks using any kind of http proxy. You need to report this problem to Apple as they're the only one who can fix the bug. The more reports, the more likely Apple is to fix the bug.
GlimmerBlocker-1.4.16.dmg (release notes). When installing GlimmerBlocker, you might be prompted to install Java. Some users need to re-run the GlimmerBlocker installer after the java installer is done.
No version of GlimmerBlocker is compatible with OSX 10.4.
Easy to uninstall if you don't like it anyway.