Looks exactly like what I did with
VanillaSoap.
The main gist of it is the main content has a background with the bg colour and shadow on it which is tiled vertically. The main box has padding on either side to allow the shadow to sit there (this is the outer shadow by the way - it's a PNG with transparency gradient for the shadows).
The inner shadows is achieved by cheating - it's just two absolutely position divs inside the main content made to stretch the whole length of the main content.
Dig round the code of VS if you want a better explanation of how exactly I did it

(note: there's probably better ways, VS was coded on a drunken afternoon last weekend).