title: Using themed css files requires a header control on the page. (e.g. <head runat="server" />)
body: <p>I'm working on asp.net web project. When I run the project, It works correctly. But In server, I got the following error. How to solve this problem?</p>
  
  <pre><code>Using themed css files requires a header control on the page. (e.g. `&lt;head runat="server" /&gt;`).
  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. How to solve this problem?
  
  Exception Details: System.InvalidOperationException: Using themed css files requires a header control on the page. (e.g. `&lt;head runat="server" /&gt;`).
  
  Source Error:
  
  An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
  
  Stack Trace:
  [InvalidOperationException: Using themed css files requires a header control on the page. (e.g. &lt;head runat="server" /&gt;).]
     System.Web.UI.PageTheme.SetStyleSheet() +2458406
     System.Web.UI.Page.OnInit(EventArgs e) +8699420
     System.Web.UI.Control.InitRecursive(Control namingContainer) +333
     System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,  Boolean includeStagesAfterAsyncPoint) +378
  </code></pre>