To be fair, their javascript mousewheel hackery breaks mousewheel scroll on all three major browsers. I guess they think people still click and drag scroll bars, so didn't run into the scroll wheel problem during cursory "testing".
There's another interesting bug, if you click on the thin part of the scroll bar, below the thick bar representing visible content, the bar centers on where you click. If you then click above the thick bar, the top of the bar moves to where you clicked, rather than centering on where you clicked. Apparently the developer(s) believe that consistency is the hobgoblin of little minds (either that or testing is).
On mobile (android), that scrolling section is disabled and all the content displays normally.
@dimitry it's not 1px, even in IE, when I view the page. They shouldn't have tried to make a custom scrollbar without more testing, but they evidently thought the stock scrollbar look didn't measure up to the grandeur of the rest of the microsoft openness page.