Is there any interface to submit data ? Add categories ? Add items ? About page 217 there is info, that administrative part of code allows to do so, but whole output is:
Store Inventory
Category

Well, there is some problem with Firefox (2, 3 I have checked on both) with change of display property. Shop works on Opera, Internet Explorer, Chrome, even on Iceweasel for linux, but not on Firefox on windows. I do not know how to fix it, but I post here as noticed that is not common problem.

I have this same problem with Firefox. I don't know where to start to try to fix it.

Any idea?

Thank you for pointing this out about the browsers.
This is useful information for anyone starting to do the shopping cart.
I have a post Chap 8, Shopping Cart, issues, Ajax, missing file - checkout.php
which I hope will be helpful to both of you.
I know it has been a long time since your post came out,
but I think the post will answer these questions.