Take this site with a huge grain of salt. It generally rewards easy professors and punishes hard ones. Many of the best teachers at my school had so-so records on the site because they weren't afraid of failing people. People that do average or well in a class are much less likely to fill out the form on that site than someone who's looking to spite the professor that just failed them.
The corollary is also true, that easy but useless professors tend to have high scores.
The best advice for picking professors is to make friends with people in your program that are further along than you and ask them who their favourite professors were and why. If they say he was great because the class was easy and you got an A avoid that professor, you won't learn a thing. If they say something like well I didn't get a great mark but I learned so much that it was worth it that's the professor you want.
The corollary is also true, that easy but useless professors tend to have high scores.
The best advice for picking professors is to make friends with people in your program that are further along than you and ask them who their favourite professors were and why. If they say he was great because the class was easy and you got an A avoid that professor, you won't learn a thing. If they say something like well I didn't get a great mark but I learned so much that it was worth it that's the professor you want.