To change the default browser in Visual Studio 2010 you can use the excellent World of VS Default Browser Switcher extension.
It adds a browser chooser toolbar (View –> Toolbars –> Default Browser Switcher) and ‘View In Browser’ options when .aspx files are right-clicked.
The Toolbar is especially useful for ASP.NET MVC projects as they don’t allow the standard ‘Browse with..’ right-click options

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