Seems like you must recheck others ignorance:

http://blog.whatwg.org/the-road-to-html-5-contenteditable#hi...

Also you can see latest commits about it. Or you want a comment saying: contentEditable was working since Google Chrome x.y.z.d, Mozilla Firefox a.b.c.d, Opera t.y.u.i, unknown browser p.l.m.n, etc?