I went to visit a friend in the US for 2 weeks in May and was planning on flying over again in November for another 2 weeks. Is this allowed? I know you're only allowed to visit the US for 90 days before you have to leave. Does this mean I won't be allowed to return in November?
If you did indeed leave after two weeks the first time, then there is no problem with visiting again in November. Since you mention "flying over", I'm assuming that you normally do not live in North America.