The wide left nav was the entire reason for the site redesign!
Well, everything is supposed to stay where it used to be and look more or less the same. The reason that forced the change: some of the new classes in the C++11 standard have been added to the reference (the containers), and this required wider navigational menus (due to the new class names being considerably longer) - the old layout could not accommodate for this.
I hope you like it!
but if you don't... there is still a way to see the page with the old layout... just find the link!