WordPress pages, design shift

I have a wordpress based site http://www.crystal-utada.net as you see the site is layout nicely and kinda plain but I like it that way anywho as you see i have many pages and when i add a new page my design shifts yp make room for the new page which i clearly do not want is there a plugin to better mange pages or a alternative way of organixing my pages
Theme I am using is Fspring 1-0