Well...
I'll cut to the chase, Here's what I didn't like about it:
No music
You have to click check and next whilst being timed
Basic layout
Didn't accept 010 as a valid answer for 10 (a bit petty but that did annoy me a bit)
Same type of sum every time, eg. first 2 runs through were addition, then 2x multiplication, then 1x subtraction (where each answer was a negative).
I've seen maths quizzes done before a lot more professionally, and I think you could do it, with a little more time and perserverence. Work on some of the stuff I've pointed out and the most important of all of them I think is to ditch the check and next buttons, and use enter. (Also, autofocus the cursor in the answer box, saving another click)