Right sidebar width

I used the layout called Three columns (style 1). I need to change the width of the right sidebar to make it skinnier.I don't want to use the style 3 because although it has 3 equal columns, the middle column gets too skinny with that style layout. Please let me know how do I change the width of the right sidebar? Also, how do I make the adverts that I added into the right sidebar, appear with a white box behind them, it is a Ad King Pro widget that I added to the right sidebar, and it doesn't show up in a box like the other widgets do.