This is a great website to test if a public website is responding. http://downforeveryoneorjustme.com/ I am not sure what mechanism it really uses to test if a site is responding, if it is a ping test or if testing actually does an html GET. Anyways, this site may be a worthwhile addition to your network troubleshooting toolkit bookmarks.
Thanks for your time. Let’s be good network citizens together & practice safe networking!