The page we are building has two distinct sections or divisions. Before we can easily define what they should look like, it helps to create the divisions and add some content to them. Since we're using Style Sheets to define how the page will look, including the layout, the divisions won't look exactly like my final page until later.
First add the two div elements. Give them both a unique id using the id attribute. I like to identify my divisions based on the location or function. So a column on the right might have the id "right". Or a navigation header division might have the id "header". Add two div elements to your document and label them "nav" for the navigation column and "main" for the main column.