I would rate this web 4.5 out of 5 for,
1. good and simple interface
2. very good content
3. correct ans
4. quick ans to the query
5. very competitive price.
I would have give full 5 star if they have added the explanation, all though, I feel this is good in a way as this made me to search on the wrong questions and analyze at my own, which ultimately a good learning, however little time consuming.