From Chironex Software:
A great tool for Web developers, Browser Spy is an Internet Explorer extension that provides a number of useful tools to help speed up Web development. There are currently two extensions that make up Browser Spy--Inspector and Source View. Inspector is a powerful way to easily access common objects on a web page including images, flash, scripts, CSS, and hyperlinks. You can easily save all of these items to file or copy there URLs to your clipboard. Each item is also shown in an easy to understand preview area that gives a preview of the item.
Source View is the perfect tool for Web scripters who need to get into the code. No more repetitive "right-click view source" style tasks. Now you can see the Web page source as you browse the Internet. Source View also allows you to configure your own custom tools to allow for Web page editing and other useful functions. Also you can change your display resolution from within your browser so you can test your Web pages in different resolutions.