Select whether the Header and Footer will span the full width of the browser window (option 1), or whether they will have a maximum width of 1728px (option 2). If option 2 is set, the page background will be visible at the vertical edges of the window, when the window resolution is greater than 1728px wide.
Option 1: Full width header/footer
Output on a Mosaic site: Option 1 - Full width header/footer
Option 2: Maximum width of header/footer limited to 1728px
Output on a Mosaic site: Option 2 - Header/footer limited to a maximum width