Developer Toolbar for Internet Explorer 6 and 7

Microsoft has released the final version of Developer Toolbar for Internet Explorer 6 and 7 which provides many features for exploring and understanding Web page. This add-on enables users to analyze the code of a web page by color coding the HTML source, matching CSS selectors to page elements, can modify the document object model of a web page, determine and indicate the specific elements on a web page, validate HTML, CSS, WAI, and RSS web feed links, Display image dimensions, file sizes, path information, and alternate (ALT) text, Selectively clear the browser cache and saved cookies and more.

Source: Betanews.com