A15" diagonal screen has much less area at 16:9 than at 4:3. That's why it's cheaper.
Anyway, how can you say websites are more horizontal than vertical? On any kind if site, you are much more likely to have to scroll vertically to get what you want. That means increasing visible vertical space improves your experience more than adding horizontal space will.
Edit: I run my web browser in the left half of my 1920x1200 screens because when I maximize them I feel like the window is much too empty. So there's room for preferences, of course. But I think most content on the web is taller than it is wide.
Anyway, how can you say websites are more horizontal than vertical? On any kind if site, you are much more likely to have to scroll vertically to get what you want. That means increasing visible vertical space improves your experience more than adding horizontal space will.
Edit: I run my web browser in the left half of my 1920x1200 screens because when I maximize them I feel like the window is much too empty. So there's room for preferences, of course. But I think most content on the web is taller than it is wide.