Check out example codes for "how to do Employing defensive code in the UI to ensure that the current frame is the most top level window". It will help you in understanding the concepts better.

Code Example 1

<system.webServer>
  ...
  <httpProtocol>
    <customHeaders>
      <add name="X-Frame-Options" value="SAMEORIGIN" />
    </customHeaders>
  </httpProtocol>
  ...
</system.webServer>

Code Example 2

Protected Sub Application_BeginRequest(sender As [Object], e As EventArgs)
  Response.Headers.Remove("X-Frame-Options")
  Response.AddHeader("X-Frame-Options", "DENY")
 End Sub

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