If the Explain feature does not show your example, but only shows the deafult example (10.11.12.13) then likely yor browser is blocking cookies.
If you are using Internet Explorer, you should see something like this:
. If so, double click on it. This screen should show up:
Now double click on the line that says "http://subnetmask.info/". It should bring up this screen:
Now change the setting to "Always allow this site to use Cookies" and click on OK.
Click OK again and refresh the screen.
. If so, double click on it. This screen should show up:
