We typically achieve an uptime of over 99.9 percent as:
The vast majority of our software updates are made with zero downtime, so our scheduled downtime is very low)
We have numerous automated tests and monitors that regularly check the site, so any unscheduled downtime is kept very low
While our site is almost always online and operational, we don't guarantee a certain uptime as there are a number of factors outside of our control. These include the data centers that our servers are hosted on being operational, and the network between the data center and your machine working as expected.