Forum Moderators: buckworks
With 100 very similar products, show many on a page; you need users to be able to compare relatively quickly without getting frustrated. [e.g. ebay]
With 100 quite different products, you should have sub-categories leading to pages of about 10 products each.
I've not tested it but I base it on showing the visitor only the product options they are interested in. If I want a widget, show me a page of a dozen widgets rather than page with six-dozen general gadgets, of which a dozen are widgets.
So make the div's width large enough to fit 4 across your normal large screen and then for users with smaller monitors it will fit either 2 or 3.
That will make an even 3, 4, or 6 rows depending on the size of the user's monitor.
Idk if I look into it too much, but that's just my theory :-o
Edit:
Make that four consecutive factors if you include 1 :x. User's with REALLY small monitors can get 1x12 :}
Selecting a reasonable default setting is important, but if you have any large categories with lots of products, user options are just as important, IMO.