This is a simple script that lets you view any webpage in multiple screen sizes, simulating the viewport of different devices. It works by generating a custom bookmarklet containing whatever screen dimensions you're interested. You can then just click the bookmark to view any current webpage in a variety of sizes. Simple!
Check out my site for a working version of the module: http://www.benjaminkeen.com/open-source-projects/smaller-projects/responsive-design-bookmarklet/
1.0 - Initial release - Jan 28th, 2012
Ben Keen @vancouverben