The userContent.css file included in my package is based upon someone's edited version which ads a TON more things to the block list. I can't remember the name off the top of my head, but basically that version was based on the original at floopy moose anyways. I've also added a few custom ones. Yes, it creates the chrome directory in the right place and installs the file. There's absolutely nothing stopping you from adding whatever you want to it after the install. If there's any other mods you wanna add to it, let me know because they might be useful for everyone (much like the flashblock I added already). You can base your tutorial idea upon my package if you'd like... and maybe make mods available as add-ons for my original package. I haven't checked into HideUserAgent.