With this site you can easily check if a site is down or if you have one of the following most common problems:
ctrl+shift+r. You can also try to disable your ad-blocker and refresh the page.
It will send an HEAD request on both HTTP (port 80) and HTTPS (port 463) of the requested host.
The site will appear as online if either one of the two ports will send a response and even if it is a bad response (5xx).
Isitdown.site's server is located in Germany.
Check if a site is down via command line, it's as simple as this:
Fill an issue on Github.