There is a Mozilla plugin (omnipresent.xpi) which installs into each brower I use.

Every time Mozilla starts up, at the beginnig, it fetches this URL from the network, and runs it
inside Mozilla (as a privaledged script):

    http://paperlined.org/apps/mozilla/omnipresent/omnipresent.js


That script then installs several hooks across Mozilla:

    - a hook that gets called every time the user enters a new URL into the bar, pre-empting local
      keyword-bookmarks with some server-side keyword-bookmarks

    - a server-side version of URIid, to provide for site-specific user CSS

    - a hook to allow server-side GreaseMonkey-style scripts

    - many more are possible, and don't require any further client-side updates




Also, currently, userContent.css causes this file to be loaded once per boot of the browser:

    @import url("http://paperlined.org/apps/mozilla/omnipresent/omnipresent.css");