whats the little green light for?

[bob_bobart]

whats the little green light in th box to the left of the post for?

[Blixinator]

It means you are online.
If it is grey, you are offline.

[WaterZoma]

Just because it's grey doesn't mean they are offline. It could mean they are invisible.

[Impulse]

And, for the moderators, red means invisible.