The problem is, I think, the 2d knapsack problem. In case it's of interest: https://cs.stackexchange.com/questions/1478/algorithms-for-t...

Edit: looks like the million dollar homepage is probably a bit more complicated than 2d knapsack, somewhat like tetris.

Another edit: looks like the only non-rectangular space sold on the million dollar homepage was the last space (as specified in the top linked article). So perhaps 2d knapsack is appropriate. It's late here.