@Steve Goldberg how can administrator know that when the website is getting down? is there any notification will be sent by NetSuite.

I don't think we monitor customers' sites but they are free to do it themselves. There are plenty of services out there that will do it

i don't know about netsuite sites, but there are plenty of 3rd party services that will monitor if your site goes down. Websitepulse.com is one I used to use, but I'm sure there are tons of them now.