As the post says you can make the whole page in HTML including a header and footer. That is the whole point of the guide… To make the custom page look completely different than the rest of the blogs theme.
While there is a way to add different header and footer images and or styles to a theme in the stylesheet, it is not something easily explained. But basically you would have to add the new/different css code in the themes stylesheet and then call for it in the custom page template instead of the original.
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Rinoplasti