If your website installation has more than one site set up, you can easily switch from viewing a page on one site to how it might appear on another site.
To view another site, simply choose the site you want from the Switch Site Menu on the left side of the Main Site Editor Toolbar.
In addition, iAPPS will allow you to see how page content will look on a specific device or for a specific audience segment. See "Devices and Audience Segments"