ASP.NET sequential layout problem

This is a bit hard to explain. I have a website with a lot of links to other webshops, each of these webshops are grouped by a category. I want to make an "efficient" layout, saving screen real estate. I have tried using a listview/gridview but it seems to use too much space when there are only a few items below each category. All my rows have similar height, and thus using too much space when there are only a few shops in a single category.

What i got:

GROUP 1      GROUP2       GROUP3
shop1        shop5        shop7
shop2        shop6        shop8
shop3                     shop9
shop4

What i want:

GROUP 1      GROUP 2     shop8
shop1        shop5       开发者_如何学JAVAshop9
shop2        shop6       shop10 
shop3        GROUP 3     GROUP 4
shop4        shop7       shop11

that is i want to save my screen real estate doing it this way, anyone got a solution to how this could be done?

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Maybe you can achieve it with CSS. But I'm not sure how

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Solved using datalists with columns, but then still not solved the issue on compacting the layout