It may be my setup (FF.9.3 on WinXP), but if you notice it too, please mail me your specs. For now, there's nobody having the same problems, so I consider this project as done.

The Gecko render-engine seems to show one pesky bug I never expected.

See this list:

Now, users of Firefox/Win will notice a flicker in displaying the :after { content }. Opera/Win does this perfectly, not flickering at all, and Safari doesn't seem to worry. Neither do Firefox/Linux and Firefox/Mac.

Exact specs: it only seems to happen in a combination of content + background + display: block.

Now, anyone knowledged enough to submit this to the Mozilla Bugcentre?

This disovery (or how do you call it) has been made by , and he loves your response.