Building Better HTML5

E9 features updated and new developer tools, including a new network analysis tab, updated DOM and CSS inspectors, a script formatter, debugger, and profiler, tools that help developers preview their sites in IE's different browser and document modes, quickly clear the browser cache, validate HTML, and more

http://blogs.msdn.com/b/somasegar/archive/2011/04/07/building-better-html5.aspx 

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samitha