Way, way back when I took psychology, I remember learning that it is almost impossible to design a true IQ test - most of them turn out to be tests of knowledge. As you get older, you gain more knowledge, so in tests on knowledge older people are bound to do better than younger ones. A real IQ test is supposed to test how your brain works to figure out problems, not how much you know. It is also highly inaccurate to give an IQ test to anyone over the age of 16, because at the age of 16 your brain is mature enough to use all types of reasoning, and as you get older your greater knowledge will skew the results. A true IQ test is administered one on one so the tester can see how you approach a problem, not whether or not you have a memorized answer.
In addition to all of this, in more recent times, scientists have identified different types of intelligence - like you could be very advanced at solving analytical problems but not have any common sense. Some people can absorb vast amounts of knowledge but not be great thinkers.
My oldest daughter was tested when she was 7 and her IQ was determined to be over 140. However, she doesn't have much common sense and she has made poor life choices. When she was tested, the school warned us that kids with very high IQ's are more likely to use drugs, battle depression and commit suicide. She did well in school, of course, but she just took the LSAT and although she scored well, she did not score high enough to get into a top tier school.
My son, on the other hand, was never identified as being gifted, flunked the 8th grade, barely made it through high school, and now runs a highly successful website. His work involves writing complex programs and continually solving problems which most people would be incapable of, and most people who know him through his work think of him as highly intelligent.
An online intelligence test is just supposed to be fun, like those tests to find your personality type, or the best type of spouse for you that you always find in magazines. They are not scientifically designed. I hope this makes you feel better.