The DOM spec has added an innerHTML property to all elements.
Unfortunately, this breaks Rico LiveGrids, because _getEncodedContent in ricoCommon.js assumes that non-HTML elements do not have an innerHTML property and has different behavior for elements that do have the property and elements that do not.
See https://bugzilla.mozilla.org/show_bug.cgi?id=870709#c7 for more information. This is causing content using Rico to show incorrectly in Firefox 20 and above.
See closed patch #11 for a patch to restore the expected behaviour.