Accuracy of online tests

I recently just to find out how much I had changed since leaving school took another career test as most of us would have done in 7th form. This was at http://www.futureproofyourcareer.com/?hop=rjells and this made me question how accurate online tests truly are. I have always been skeptical of the internet and how accurate the information being presented to people online was but this had a particularly strong resonance in this case. This was promarily because after I received the results it said that i was most suited to a job in Mathematics or Engineering, previously I had taken around 3 -5 of these tests and they had all concluded taht i was more suited to jobs in social sciences. This also made me question the ability that online tests because i have never been particularly good at maths or sciences, particularly physics. Maybe I am simply placing too much empahasis on how accurate the information that we are receiving through sources like these and how potentially this could alter someones decisions in life, but i believe that although I know the internet will never produce truly accurate information in all cases, or even any cases tests that have implications like this must be as close to accurate as possible because of the impact they can have on people.