There are really two attributes involved, designMode and contentEditable. A brief and extremely biased timeline of standardization.All major browsers support this now, including Firefox 3, Safari 3, Opera 9, Google Chrome, and Internet Explorer (since 5.5).
The feature of the day is contentEditable, by which I mean client-side in-browser 'rich text' editing. Welcome back to my semi-regular column, 'The Road to HTML 5,' where I'll try to explain some of the new elements, attributes, and other features in the upcoming HTML 5 specification.
