Why do I get a margin around my site when I publish?

I have developed my site in AS3/ CS3, and when I publish I get extra margin around my site. It’s not even centered!!! My background is the exact size as my stage, and in development when I test my site, it’s perfect. What happens when I publish? Why do I get the extra margin, when the html is run??? … and it has to do with my stage, since I can control the color on the properties panel, but not the size??? Please help!!! I really need to get my site up.

I thought of using match content in the properties panel of the stage, but I still have problem. Some of my animations start outside of the stage and this does not solve my problem either!!!

Thanks much.