frameborder attribute of the iframe tag (HTML 4.01)

The frameborder attribute controls the border appearence of the iframe tag. It only has two possible values: 0 or 1. It's really up to the browser to figure out how the border will look, and therefore it varies from browser to browser, but you can turn it off by setting the property to 0. If you set it to 1, some kind of border will be rendered.

Consider these two examples, where the first window has its frameborder set to 1, while the second one has its frameborder set to 0: