You are about to start on the road to having a web presence and are talking to a number of design companies about your site.
Save yourself some grief and negotiate the following:
* At the end of the development you get ALL source for your web-site, including the source for all media, both static and interactive
* If you are registering a domain name, that domain name is registered under your name, not the development company
* You are not tied into proprietary software owned by the development company