Site Structure Preview
The Difference Between Fixed and Fluid:
What this dynamically changing image does for you is provide a quick reference as to what the "Site Structure Options" to the right will do based on their settings.
The horizontal strips of dark and medium gray represent the Header, Navbar and Footer areas. As you can see, if "Fixed Design" is selected the #wrap width is fixed resulting in the Header, Navbar and Footer areas being "fixed" inside it, but if "Fluid Design" is selected then the #wrap width is set to 100% resulting in these areas becoming fully fluid.