1. I have inserted a png which is fine when I view the web site in a browser but while it is in the design page there is a large block aroud it. How can I get rid of this ?
2. Same with inserting video, there is a white area to the right and below the video

3. Yet another question. I make a shape then select to Buttonise it. I enter the Text for the Button but the text has a shadow. How can I get rud of this?

And another,
Im finding that the buttons I make are not sharp when they are displayed in a browser. Is there a resolution issue I need to be aware of because as it is the end result looks pretty crappy

In VSD, PNG files will have a black background, they'll be transparent in preview and on the web. The black or white background just shows the bounding box for that item.

I've not done much with the Buttonise feature, but in general, you would go to Effects (top menu) and uncheck the drop-shadow option. As for the third issue - is it the text or the button (or both) that aren't sharp? Maybe someone who's made more use of the Buttonise feature can help you with this