The green light.

[Enrique]

Hi: can one choose not to be seen, I mean, the users can't tell if one is online or off-line (green LED like light).

[Chris]

I don't think so. But you can log out to achieve that effect - you just can't post while logged out.

[Enrique]

And what if I, without logging out, cancel execution of the web browser (File>Quit or File>Exit)?

[Chris]

That has nothing to do with it. It doesn't really know you are "online". It basically just means you've done something on the forum during the last few minutes or so. If you leave the forum up but don't do anything for a while, it can't know you are still "online."

[Enrique]

Yes, that's very illustrative. Thanks for your help, Chris. On the other hand, now I realize your interface, that of BRS forum, is the same as that of many other quality fora, starting by the graphical design.

[Chris]

Yes, vBulletin is one of the most popular choices for forum software out there.