This website (Mini Physics) offers O and A Level physics revision notes for you to learn Physics online. O Level is equivalent to American High School Diploma and A Level is equivalent to Advanced Placement.
If you spot any mistakes in my explanation, please email the site administrator at firstname.lastname@example.org with the relevant web address and explanation. If you feel that you can offer a better explanation for some of the topics, please do email with your explanation.
In general, the difficulty:
O Level(Secondary School) < A Level (JC) < H3 (JC) < University