This document extends XHTML 1.1 via an internal subset of the DTD. It adds the target attribute to the anchor element. The link in this sentence should open in a new window.
This document validates as XHTML 1.1.
The DOM thinks this document is in mode.
This box should be equally as wide as the red lines above and below it. Equal lengths suggest that your browser is in Standards Mode. A box that is less wide than the red lines indicates a browser in Quirks Mode.