Two container div to bring the same level
It always comes back before, that the programming of web pages 2 standing next to each div container has. Take some a classic HTML web page. There is container div to the left as responsible for the content and the right div container for the menu.
It is now, however, at short, and long posts (on the left) before, that the height of the two div containers are not the same and, accordingly, the background color (or graphic) are not brought to a common denominator.