In the web.config file, after the closing system.web structure and before the closing configuration structure place the below code:

After The Line

</system.web>

  <location path="PageName.aspx">
	<system.web>
	    <authorization>
	      <allow users="*" />
	    </authorization>
	  </system.web>
  </location>

Before The Line

</configuration>

Hope that helps...