Coding Problem: Cannot view XML input using XSL style sheet.

I had just begun my web page applications programming, and I came across this problem right away:

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The XML page cannot be displayed
Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later.
A name was started with an invalid character...

<%@ Page Language="C#" ...

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I searched msdn, and below is what I found that worked for my case, which is run at the command prompt:

%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe -i


Maybe you would come across the same problem, and the solution may be the same... who knows?!