Size of gallery in wordpress.

What to change to fit the gallery in wordpress Page over the whole page.
And how to change the css so that when the page is bigger it doesn't disappear under the side bar.

See http://www.petervanroon.eu/wpg2

So the answers i need are :
How to use the whole page width
How to make go to the next line instead of disappearing behind the sidebar
Or how to get a option to scrollto the right if the page is bigger.