How activity is calculated:
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 30 minutes.
These are the ranks:
Rank
Description
Tag
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.
You can read the thread relarted to your question for discussion:
https://bitcointalk.org/index.php?topic=178608.0Search the forum with the search function when asking questions because it has a high chance of being answered already, either through official documentation or unofficial. Reading 'sticky' threads on every sub-forum may be a great start, especially here in the 'meta' section has it has things
related to the site. This question has been answered many times and has a lot of threads which are duplicates, including this one.