FIFA Math
Following is what FIFA use to calculalate the rankings. Note that they consider the last "8 Years". This is the biggest problem. A helluva lot can happen in 8 years. If the rankings are using results from 8 years ago they will hardly reflect todays better teams; for example, Turkey. So, I really don't know what significance the rankings have. One result such as the U.S. beating Portugal probably doesn't have that big an impact. The rankings are totally meaningless at any point in time, so who the fuck cares about them.
The relevant web site is at the bottom of the following info.
Taken into consideration for the ranking are all international-A match results over a time span of the last eight years:
World Cup finals matches
World Cup preliminary matches
Continental championship final matches
Continental championship preliminary matches
FIFA Confederations Cup matches
Friendly matches
The ranking list is produced by a computer program which assigns a team points for every match, according to clearly defined criteria. The factors taken into consideration are:
Winning, drawing and losing
Number of goals
Home or away match
Importance of the match (multiplication factor)
Strenght of the opponent
Regional strength (multiplication factor)
http://www.fifa.com/rank/index_E.html