make flash fit in browsers

I want my flash website to correctly fit in different browser windows. I just upgraded to Flash CS5 from Flash CS3. I also now have a Mac instead of a Dell Laptop. So, there are new Flash tools I have to come up to speed with. Does anyone have a recommendation to get my flash website to show up correctly on different browsers and monitor sizes?

Thanks for your help.

OH, one more question. I created my flash website using some AS2. Can I add an external SWF that is done in AS3?