IE HTML Element Spy can be downloaded here. Click on the Getting Started link for a screenshot.
IE HTML Element Spy is tool that will help you to understand the structure of existing pages on the web, it is very easy to install and use, and, it is a FREEWARE! That means you can download and use it free of charge for an unlimited time.
Additionally, I like to have portable applications. Using Universal Extractor, you can extract the contents of the setup file and run IE HTML Element Spy without installing.
Edit - MODIv2 is another great tool, and it supports most major browers . (also referenced in this thread)