Both. I have two horizontal and two vertical (from left to right: V, V, H, H). The last horizontal I use mostly for IM windows, comparing versions of a page in

Both. I have two horizontal and two vertical (from left to right: V, V, H, H). The last horizontal I use mostly for IM windows, comparing versions of a page in the browser, etc. Sort of like my monitor "scratch paper" -- I could do without this one if need be. The two vertical make it easy to compare code and work on two files side by side. The first horizontal is great for checking UI work in the browser.