In the past I'd noticed strange behavior whenever the Mouse is held over thread introduction presentations (in the forum thread-list).
1) In some cases, the text that shows up in then pop-up box doesn't change when moving it over a new thread. In other words, the text that pops up is simply the same text as showed up for the previous thread. Moving the mouse over a third thread triggered an update, but then that text repeats over the next thread.
2) Sometimes source code appears instead of regular text (see attached image).