Ideall you would keep the same basic layout structure from page to page. For instance, you would have:
<div id="header">Your header and or site logo</div>
All your main content goes here.
<div id="sideBar">Side bar menu here</div>
Then your stylesheet would contain stylerules for all your divs. If some div element changes on another page, you simply div it an id or class and style that id or class.