overflow: visible
The box below (light gray background) is supposed to be only 100 pixels in height, but because a value of visible is used, the content forces the box to be taller.
This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5. This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5. This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5.

overflow: hidden
The box is exactly 100 pixels tall, and the rest of the content is clipped — not shown at all.

overflow: auto
The content is clipped, and a scrollbar is added if necessary, so that users can get to the rest of the content.

This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5. This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5. This is a paragraph of text to show how overflow works — at least in Internet Explorer 4 and 5.

If your browser doesn't support this CSS property, click here to see what it looks like.