Rank
Brand New:   0 posts, gets 1 gold coin under his name.   
Newbie:   (none), gets 1 gold coin under his name.   
Jr. Member:   Activity: 30, gets 1 gold coin under his name.   
Member:   Activity: 60, gets 2 gold coins under his name.   
Full Member:   Activity: 120, gets 3 gold coins under his name.   
Sr. Member:   Activity: 240, gets 4 gold coins under his name.   
Hero Member:   Activity: 480, gets 5 gold coins under his name.

The activity number is determined in this way:
time = number of two-week periods in which you've posted since your registration
activity = min(time * 14, posts)

Activity is updated every hour.