Aligning a document

Can anyone tell me what is the best size for a document? I use the default setting in flash but when I import it into dreamweaver it allows the scroll bar in the window to become active and allows the user to scroll a little. In the publish settings in flash I have set it to 100% and 100% AND CENTRE,CENTRE - but once the doc is in dreamweaver it appears on the left once published…can anyone help?