I have installed this mod and it don't seem to work. Is it right that this mod will not work against people using sites like urlbrowse.com and proxy911.net against my website?
That is indeed correct. CGI proxies - as both of those are - don't have a universal way of being accessed, whereas HTTP proxies do. CGI proxies can be placed at any particular director and trying to guess which directory they're in isn't really feasible. For HTTP proxies, you don't have to do any guess work - just send a specially crafted HTTP request to it and if it's an open proxy, it'll work.
If you wan to detect CGI proxies, IP Unmasker
can do it. I need to release an update, but have, thus far, been more focused on other things.