xmlns:mc=”http://schemas.openxmlformats.org/markup-compatibility/2006 is the XAML compatibility namespace. You can use it to tell the XAML parser what information must to process and what information to ignore.
http://schemas.microsoft.com/expression/blend/2008 is a namespace reserved for designspecific XAML features that are supported in Expression Blend and Visual Studio 2010. Itâ€™s used primarily to set the size of the design surface for a page.
mc: Ignorable=” d” d: DesignWidth=”640″ d: DesignHeight=”480″