People can't seem to reach my websites

I have a frequent problem where people say my site is down even when I see no evidence of this on my end.

The site is www.lubasi.org. Can anyone explain possible reasons for why my web host says the site up, I see that the site is up when I go to the site, yet other people have trouble accessing it? What do I tell the people who can't see the site how to fix this problem? I don't think so many people are lying.