float trouble in firefox/opera

This is my first site, first exposure to CSS, first exposure to HTML for that
matter. Perhaps I bit off more than I could chew, but I'm on the pleasant side
of the learning curve now.
According to the webhost stats for my client?s site, 90% of visitors use IE,
so I designed with that in mind. I talked the business into going from a 6 page
shtml fossil to a new site with webstore. I'm learning ASP for CartWeaver, so
the webstore won't be implemented until year end. When it's functional, I
anticipate the client will have a broader range of browser visits, so I don't
want the page to fail in Firefox or Opera. I'm waiting for more data from the
client, so the site is incomplete. There's enough in place, however, that my
novice errors should be obvious. The html validates as 4.01 transitional. The
css validates, although it?s a little convoluted and I?ll need to clean it up a
bit.

http://www.con-cor-co.com/
http://www.con-cor-co.com/concor.css

Please advise on correcting my css or html to make the site Opera/ Firefox
friendly. Also, please give criticism and compliments as you see fit. One last
question: I haven't settled on a price for the site, so I'd like some input on
what to charge. The web store will have about 500 items for sale, and I have to
build the database from scratch. Thanks in advance for your help.