This red area is a section. The background color property has been set to this color. Sections can apparently use different template-based formatting to change their appearance. Inside the section, this is where the first textbox landed.

This is the second textbox. Wow these sections sure burn a lot of graphic real estate.  Note, the "body" of the page (where containers like textboxes normally live) is below. The "section" container appears to be independant of that.