Edited to get to the point more quickly
A) What exactly is post rank? (To clarify my question, I searched post rank and found stuff about the liscense, that is not what I am referring to. Click 'My Profile', click 'favorites', if you have users selected as favorites, they will have a post rank next to their name. Seems to have nothing to do with counts. Ranks are 0, 32, 64, 128.)
B) How is racing liscense determined?
EDIT: I found the answer to my second question (sorry I missed it).
Drows responded to someones question saying:
Driver's Permit: 1 - 15 posts
Driver's License: 15 - 50 posts
Racing Permit : 50 - 80 posts
B-class Racing License: 80 - 120 posts
A-class Racing License: 120 - 175 posts
S-class Racing License: 175 - 300 posts
U-class Racing License: 300 - 400 posts
R-Class Racing License: 400 - approx. 450 posts
Forza Community VIP: approx. 450 - 5000 posts
FM.net 5k posts Club member - 5001+ posts
Note: I changed the threshold between R-class and VIP from 427 to approx. 450 on August 8th. That is my best
approximation of the actual current threshold. Thresholds do change and can change at any moment without my
knowledge.
C) What are the green rectangles under my avatar?
EDIT: Thanks Fast Freddie and Moulsdale for your help.
No bars = Not Ranked 1 bar = Top 500 Contibutor
2 bars = Top 200 Contributor
3 bars = Top 150 Contributor
4 bars = Top 100 Contributor
5 bars = Top 75 Contributor
6 bars = Top 50 Contributor
7 bars = Top 20 Contributor
8 bars = Top 8 Contributor
bars = pips
D) Another interesting bit of info on post rank:
!Clicky courtesy of Kaiser!
Taken from a very informative thread on hyperlinking by Drows:
http://forums.forzamotorsport.net/forums/1/44966/ShowThread.aspx#44966
Love Forza, Love Turn 10, Love ForzaMotorsport.net. Thanks.
EDIT: If any mods want to delete this, because they think it will lead to excessive posts, I won't be offended.

GT: Displace