As soon as any site starts gettng high traffic, it starts monetizing in every possible way.
same is with speedtest.net
this is currently the no.1 speed test service.
accurate though full of ads.
their are high chances of clicking ads by mistake.
they donot care about user experience!
the best alternative is fast.com by netflix.though it only shows you the download speed but that is the only thing what matters to us the most.isnt it?
I have shifted to fast.com now and do regular speed tests their.they are ad free and I simply love it!