Caret not shown for designmode iframe which is empty
I am running into the problem described in https://bugzilla.mozilla.org/show_bug.cgi?id=308736 and can reproduce the problem using Firefox 19.0 for the two examples provided in the bug posting. The bug however is marked "Fixed" in a very old version of Firefox.
This is a case where we have an iframe and it is setup to be in designmode to act as a html editor. The editor starts off with no content (i.e. the <body> element contains no children). When the user clicks inside the iframe no caret appears. If the user types even one character the caret will then appear as expected. This however confuses users since after the initial click in the iframe they should be provided some sort of feedback to let them know that they can start typing.