Internet Explorer Developer Toolbar

The Internet Explorer Developer Toolbar provides several features for exploring and understanding Web pages. These features enable you to:

• Explore and modify the document object model (DOM) of a Web page.
• Locate and select specific elements on a Web page through a variety of techniques.
• Selectively disable Internet Explorer settings.
• View HTML object class names, ID's, and details such as link paths, tab index values, and access keys.
• Outline tables, table cells, images, or selected tags.
• Validate HTML, CSS, WAI, and RSS Web feed links.
• Display image dimensions, file sizes, path information, and alternate (ALT) text.
• Immediately resize the browser window to a new resolution.
• Selectively clear the browser cache and saved cookies. Choose from all objects or those associated with a given domain.
• Choose direct links to W3C specification references, the Internet Explorer team weblog
• (blog), and other resources.
• Display a fully featured design ruler to help accurately align objects on your pages.
• The Developer Toolbar can be pinned to the Internet Explorer browser window or floated separately.

This is truly a must tool for developer and for GUI designer as well.
You can download it from: http://www.microsoft.com/downloads/details.aspx?FamilyID=e59c3964-672d-4511-bb3e-2d5e1db91038&displaylang=en

I will keep this blog updated for any new version that will be out there.