The "page within a page" look can be seen in use for many sites these days. That is when the page appears to be centered on top of a background. Despite the widespread acceptance of this new "standard," some people greatly dislike it. Although web designers and developers certainly offer advice to clients regarding how web page design is being standardized, the ultimate decision rests with the client who is paying for the service.
During my college years of studying web development, my class was placed in charge of designing and developing a site for the Information Technology (IT) department. Of course we used XHTML, CSS layouts, images, and a couple of other scripting languages--Hypertext Preprocessor (PHP) and Javascript.
Those who handled the CSS layout were surprised to find that the professor to whom final approval was left, did not at all like the centered "page within a page" look and required a switch back to the older traditional look of the page covering the screen. Clicking on the screen shot below will reveal the new "standard" centered page style that might or might not be acceptable to clients.