Every HTML tag is surrounded by a world of properties that affect how the tag appears in a web browser. Some properties—like borders and background colors—are immediately obvious to the naked eye. Others, though, are invisible—like padding and margin. They provide a bit of empty space on one or more sides of a tag. By understanding how these properties work, you can create attractive columns and decorative sidebars and control the space around them (what designers call white space) so your pages look less cluttered, lighter, and more professional.

Taken together, the CSS properties discussed in this chapter make up one of the most important concepts in CSS—the box model.