EDIT: Serves me right for trying to do too many things at once. I meant to say it supports the If-Modified-Since and Last-Modified headers, not the If-Last-Modifed header. Sorry for any confusion.
Using TCPView, I noticed that there were a lot of sockets in TIME_WAIT status. Especially on sites that had image rollovers.
I decided to add Keep-Alive connections to minimize the number of open sockets. I also added support for the If-Modified-Since and Last-Modified headers. This way cached files will not have to be resent.
Logging was also fixed to log these other statuses like 404 Not Found and 304 Not Modified.
I'm going to change the way configuration files are used in the next version. I don't like using the App.config, since it gets overwritten every time you rebuild and reinstall.
Anyway, that's all for now.