Microsoft has a toolbar introduced which is helpfull to web developers. They can check compatiblity with W3C standards for html and CSS. As stated on their website:

"The IE Developer Toolbar provides several features for deeply exploring and understanding Web pages.

• 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 800x600 or a custom size.
• 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"

http://www.microsoft.com/downloads/details.aspx?FamilyID=E59C3964-672D-4511-BB3E-2D5E1DB91038&displaylang=en