Contact form..need help!

hello,
I ahve prob with my contact form. I use the sample and yess, it works. but when i put it
in my flash website, when i click send, nothing happen. and suppose in the movie frame,
when i click send, it will move to the _nextFrame, to show the “thank you” message. and then i can click back button to return to contact form.
I find out taht somethin to do with the _root. I want to know more about _root, _level0.
what are this thing?
Thank you.