Scaling Quesion

I have a title with an anchored header at the top that should take up the entire page (it is about 10px wide on either end and centered on the page). When publishing, I select 'Scale the page to the window width.' However, when the page opens, there is a gap on the right-hand side no matter how the page is resized.

What is preventing this from displaying across the full width of the page?