A lot of RWD websites cater for 3 major breakpoints (phone, tablet, desktop) and make the design fluid between that. However, the thing that's hardly ever included is the landscape view. Rotate your phone into landscape and the website usually falls apart. Often the problem doesn't lie on the horizontal axes, but on the vertical one: there is simply not enough height to cater for the content.
How are you dealing with this? Do you include landscape view in your design process? How, and what are the biggest problems you came across?