add mime type

gistfile1.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration xmlns:xs="DotNetConfig.xsd" xmlns:vs="http://schemas.microsoft.com/.NetConfiguration/v2.0">

    <system.webServer>

        <staticContent>
            <mimeMap fileExtension=".gspl" mimeType="application/x-deflate" />
     </staticContent>

    </system.webServer>

 </configuration>