IQ testing has undergone a number of changes since its inception, most notably the addition of spatial tasks. This makes it a more thorough test and a better predictor of overall intelligence because it is not limited to just verbal and performance. Any test will have disadvantages, and all of the available IQ tests have been updated and will surely be updated again as we understand more about intelligence and how to measure it.
IQ is a measure of a person's mental age relative to his physical age. This is standardized so that a ratio of 1:1 would give you an IQ of 100.
As you grow older, your IQ would change. Those who work in the field of knowledge application would drop in IQ (due to knowledge always keep piling up). Those who work in the R&D frontier could go either way. If there is something new they found, IQ boost. If not, IQ lost (failed a rhyme there).
What I'm saying here is that don't worry about them IQ test. They say nothing about you (except whether you are more idiotic than the rest of people YOUR AGE). What you should worry about is your cognitive capacity. There is currently no accurate measure of cognitive capacity.
People, when they find out about your IQ score, decide then and there whether you're smart or dumb and immediately judge you for it. One of my best friend's IQ score is around 72, but I don't judge her or blame her for who she is. My IQ is around 123, but I don't act all prejudiced or high and mighty, whereas some people are total jerks about it and want to say they're smarter that everyone else.
Just consider the consequences when trying to determine how smart someone is based off some stupid computer program.
As with any testing that is done, IQ testing only gives the potential of a person. It can not say with accuracy what a person is capable of but can only indicate what might be possible. And of course there are cultural factors inherent in the testing itself so it might be biased.