force www in your url

Add rewrite rule to you web.config to enforce http://www.extending.nl instead of http://extending.nl

 <rewrite>

 <rules>

 <rule name="WWW Rewrite" enabled="true">

      <match url="(.*)" />

        <conditions>

          <add input="{HTTP_HOST}" negate="true" pattern="^www\.(.*)$" />

        </conditions>

        <action type="Redirect" url="http://www.{HTTP_HOST}/{R:0}" appendQueryString="true" redirectType="Permanent" />

 </rule>