Comment 1 by jteh on 2011-08-09 21:42
Yeah, I think I've seen this as well. Does NVDA+f5 resolve this? (Obviously, this isn't ideal, but I'm curious as to whether this is the same issue I'm seeing.)

Comment 3 by elliott94 (in reply to comment 1) on 2011-08-09 22:00
Replying to jteh:

Yeah, I think I've seen this as well. Does NVDA+f5 resolve this? (Obviously, this isn't ideal, but I'm curious as to whether this is the same issue I'm seeing.)

I'll report back when I manage to replicate the issue. :) Have you found a way to deliberately make this occur?

Comment 4 by jteh on 2011-08-09 22:04
No. I assume this happens on sites where there are normally levels? (It is possible to have a heading without a level, though it's very rare.)

Comment 5 by elliott94 (in reply to comment 1) on 2011-08-10 12:01
Replying to jteh:

Does NVDA+f5 resolve this?

I've just encountered this issue again, and NVDA plus F5 does in deed resolve this.

Very strange.

Comment 6 by elliott94 on 2011-09-07 14:48
Just a small update.
This seems to only happen when a page is opened in a new tab, the previous page switched back to, and the new page brought back into focus. Again, though, this doesn't always happen, and it's hard to find an exact reason why this occurs.

Comment 7 by jteh (in reply to comment 6) on 2011-09-15 02:03
Replying to elliott94:

This seems to only happen when a page is opened in a new tab, the previous page switched back to, and the new page brought back into focus.

Bingo! Thank you for this thought. I haven't been able to figure this one out, but I now have a 100% reproduceable test case. It is unfortunately due to a bug in Firefox which I have just filed as MozillaBug:686821.

Again, though, this doesn't always happen, and it's hard to find an exact reason why this occurs.

It occurs if a heading appears while the document is in a background tab.

This was fixed in Firefox 18 acording to MozillaBug:686821

confirmed.