[e12e]

Long? There's been ad-blocking proxies available for a long time. Eg: http://www.squidguard.org/history.html

I remember setting up some kind of http-proxy with local cache an ad filters in the late 90s, early 00s -- possibly squid with a plugin -- probably on Slackware. Persistent local cache of static resources helped a lot with loading sites (which doesn't really make any sense, considering browsers already had a local cache). Ad-blocking was simple -- just replacing banner.gif-s with a blank gif image or something along those lines. But it worked, and preserved the layout of the page.