Hi,
some web host provides 100% Uptime Guarantees. How can i Understand and Verify Uptime Guarantees of them.

There are two ways to find out the uptime of your host.

1) Many hosts now have an “Uptime Monitored By…” graphic on their web site from a 3rd party uptime monitor, which you can verify as proof of the host’s uptime.
2) Open an account with the host and monitor your individual web site.