IQ is supposed to be a gaussian distribution with mean 100 and standard deviation of... 16 is it? I can't remember exactly, but it's well defined as such.
Now, those stupid online IQ tests are so lame it's not even funny. I've not scored lower than 145, and I've gotten all the way up to 180 on a few. What's more, taking one test before dinner gave me a 152, and after dinner I got a 167 on a different one. Your IQ should stay reasonably stable throughout your life, so a fluctuation of 15 points (almost 1 SD) over dinner is the sign of some bad testing, or a lot of alcohol (not the case hehe).
What's more, I STILL get the emails from those IQ testing websites in my spam account saying what my IQ is, and that if I want to pay $9.95 I can get a "full detailed report" or some crap like that.
Further still, IQ tests are very shady about determining real intelligence. Earlier versions contained questions relating to pop culture (American pop culture mind you). Billy Joe Bob from Looseyanna, 30-odd years and still in the 3rd grade gains a point on Albert Einstein because he happens to watch more American TV? Sure...
Granted, it's not that way nowadays, but there are still questions as to what makes a person intelligent. I guess the legitimacy of the test is enhanced being that it is statistical; you are ranked against an average score, not against a test. Either way, too much credit is often given to IQ scores as being absolute measures of intelligence. I guess they're more of an indication at best.