As mentioned above, would probably be too slow for outsiders anyway. Plus, if you upload speed is capped by your ISP, you'll be limited not to your incoming speed but whatever they cap your upload at (as you would be "uploading" data to them to fulfill the request).
Dynamic IP can be handled with one of the many services just for this reason, however I still don't think this is a great idea anyway.
Nobody mentioned the potential for your ISP's TOS stating that you specifically cannot serve web pages (many state this) and the fact that they may block HTTP/FTP/etc ports as many do this.
All around I think it is a bad idea.