This purpose of this test is to show the current inconsistent results for using jquery UI x-axis draggable and snappable options together. Open up your Console log to see the objects/elements that are "snapped" as you drag the red square around.
With the body overflow style set to 'auto', Chrome has a bug in the sortable widget. When set to 'inherit', this bug disappears, although the sorting is noticeably slower under Chrome and FF.