Hi, there isn't a webpage. It's for testing ping, traceroute, and nslookup on the network > diagnostics page on the Shield. If you want to test an http page you can use example.com or google.com for https
Just put the test rule in services > intrusion prevention > custom rules . Now just ping the www.msftncsi.com and it should show up in your log. Just don't forget to remove the rule when you're done