Evan Goer's "Pocket HTML Tutorial: Div and Span"

The <div> and <span> tags are crucial to contemporary site design. With "id" and "class" attributes, they allow the coder to specify different presentational qualities for the different parts of the Website. For instance, it is common to have a <div> for the banner, a <div> for the body, a <div> for side-navigation, and a <div> for the footer. Since you can specify different background, color, and font characteristics for each id using CSS selectors, it is easy to create familiar webpage layouts using these tools.