I'm not so sure why the tables are showing up in firefox and not ie and will have to see the code and check it myself to work it out.
My site has tables and i can't see them in either safari, firefox or ie when i tested it, try browsing my site and tell me if you can see any in your browsers and if not then send me your code and i will have a compare to what i used or alternatively download my pages and compare them yourself.
As for shopping carts it can be quite easy to do if you use something like the software listed below and you can install it on your server and edit the pages to look how you want them to.
http://www.cubecart.com/http://oscommerce.com/http://www.zen-cart.com/Just have a look at those and decide which one suites your needs best, there are plenty more out there but those 3 are free.
Also if you have fantastico on your c-panel you may find some free opensource shopping carts that can be installed with a few simple clicks
If you want any help mate just ask and i will have a mess around with your pages for you and try and iron out the problems.
Corroder and SP are also quite good at web coding and have helped me on here in the past.