What does the + sign mean?

[china cat]

I see that after some boardies names (it's next to their names on the list of those who are logged on)

[KrisNYG]

Ohh I can answer this one!!! It means they've been added to your friends list!

Hai China!

[china cat]

hai kris :yippee:

thanks, was wondering 'bout that.

[china cat]

oh and why are there different colored dots next to our names?

[Speckta]

That indicates whether the users are currently logged in or not.