What does the new dot on the bottom left mean?
 

There's a new dot on the bottom left of the lefthand box that contains the user info for a post. Some are green, some are gray and some are red.

What do they mean?

Thanks.

user's online status.

Just figured it out. Hey, why is mine red and no one elses is? :)

I believe they mean whether the user is online or not. If you let your mouse cursor hang over one of them for a second, they'll give a little yellow textbox with info.

Because you set yourself as invisible on the boards. If you disable that, your icon will change.