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This helped but it was also a browser specific problem. &nbsp;It appears that IE9 has to sense a new page sometimes or all the time otherwise it will not work.
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This helped but it was also a browser specific problem.  It appears that IE9 has to sense a new page sometimes or all the time otherwise it will not work.

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I am having a problem with the ASP.net Web Application for Visual Studio 2012 .Net 4.5 Web Application template. &nbsp;When I try to run a session and login, I have a problem that displays the following error: &nbsp;<br />
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<b>Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that &lt;machineKey&gt; configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. </b>
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I am having a problem with the ASP.net Web Application for Visual Studio 2012 .Net 4.5 Web Application template.  When I try to run a session and login, I have a problem that displays the following error:  

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. 

Problem with ASP.net Web Application for Visual Studio 2012

The successor to Active Server Pages, ASP.NET websites utilize the .NET framework to produce dynamic, data and content-driven web applications and services. ASP.NET code can be written using any .NET supported language. As of 2009, ASP.NET can also apply the Model-View-Controller (MVC) pattern to web applications