dropping the function from the uri

[eluser]juddmuir[/eluser]
I'm building an app that includes a classifieds board, and I'm trying out codeignitor for the first time, though by no means a php newbie!

I have three questions, relating to structuring a CI site directory:

1. If I want the URI like this: example.com/classifieds/category/123_posting_title, how do I drop the implicit function "display" from the URL? I.e. the class is "classifieds", and the function parameters are "category" and "posting_title" - but I don't want the function "display" in the URL. (Yes, I have an SEO background too...)

2. The site also has non-CI code on URLs like example.com/forum - how do I prevent CI from latching on to those URLs? Or should I say, what's the best practice for codeignitor and non-CI code to live in the same site directory?

3. Where does css and javascript go in the folder structure? I'd prefer to have it outside the system directory, so that non-CI code and CI code can both share the same css files, is that good CI practice?

Thanks in advance for any replies!