Fixed white gap

Changed experience container to `display: block`, which allows clearfix to apply properly and contain the floated half sections. The half sections' parent was inner, which was not clearfixed. Window was clearfixed, but I believe that effect is negated by `display: inline-block`. The only reason other sections were cleared properly was because a block level element, an `<h2>` in most cases, was in the same container as other floated elements.

In other words, don't use `display: inline-block` unless it's needed. Maybe it's needed for some browsers to display the sliding panes/parallax effect properly, but I didn't see a difference. Tested in latest Chrome 26.