There is a bug in the display of anonymous users online today. Sometimes users are counted twice, once as registered user and again as guest.
This happens when a user logs in, browses the forum and then logs out AND does not login again on that day.
Test it: If I visit the forum, I am counted as a guest. When I login then, the guest count is diminished by one (as it should be) and I am in the 'registered users' list. When I log out again, the guest count is again increased by one but of course I'm still in the 'registered users' list - so the number of guests and total users is wrong. If I login again, the guest count is diminished once again, but if I don't, it stays as it is.
In my forums, only registered users can read, so there are very few guests online during the day. But every day in the evening the guest count rises sharply. So I suspect that those are not real guests, but users who log themselves out and don't return until the next day.
Any chance this will be fixed?

