This is one of the core principles of web design.
When you enter a new building for the first time, you try to figure out the layout of the building, often subconsciously. And once we know where the exits, elevators, hallways, etc. are, we feel at ease. When we go up a floor we expect the layout to be the same.
This is the same with websites. When people enter your site, the first thing they do is to figure out the layout of the site. Where the navigation menu is, what the major sections are, etc. As they navigate the site, they expect the layout to stay the same. If the layout changes from page to page, they get confused.
So it is important to have consistent layout across all pages. This can be accomplished first by creating a dummy page with the basic layout and no page-specific information.
Alex Calvert WMU School of Communication, Kalamazoo Michigan
June 21, 2016