title: Postback in Iframe causing Viewstate MAC error in Safari Browser
body: <p>I have 3 .aspx files. For example</p>
  
  <pre><code>GrandFather.aspx, Father.aspx and Child.aspx
  </code></pre>
  
  <p>GrandFather.aspx page has an Iframe and the iframe's source is Father.aspx. Form Father.aspx, I called Child.aspx by using</p>
  
  <pre><code>Resposne.Redirect("Child.aspx");
  </code></pre>
  
  <p>As a result the iframe content has been changed with Child.aspx. Now the Child.aspx has some form-data which are submitted in its postback. Browser IE, FireFox, Google Chrome it has been working properly but in Safari, it shows the following error,</p>
  
  <pre><code>System.Web.HttpException: A field validation of viewstate MAC. If a Web Farm 
  or cluster is hosted by this application, please check that you have to specify 
  the configuration is the same validationKey and validation algorithm &lt;machineKey&gt;.
  AutoGenerate can not be used in the cluster.
  </code></pre>
  
  <p>What can be the reason behind this problem? How can I solve it?</p>
  
  <p>I have checked the source of the Iframe and it shows always Father.aspx even after Response.Redirect.</p>
  
  <p>I am using .NET 2.0 and IIS is 6.0.</p>
  
  <h2>EDIT:</h2>
  
  <p>For first time postback the Safari browser shows the error. However, for the next try, the error goes away.</p>