99% server uptime means that in a year of 365 days, your server will be up 99% of the time, which is 361.35 days (365 days x 99%). This is not really good, because even with 99% uptime your site could be down for 4 days. It would be disastrous if you owned an online store because even an hour's downtime would cost you. Imagine, not only lost revenues, but also customers who switched to your competitors while your site was down.
Here are some server uptime examples with calculations showing what various percentages mean.
100% server uptime
Up = 365 days
Down = 0 days = 0 hours = 0 minutes
99.999% server uptime
Up = 364.9964 days
Down = 0.0036 days = 0.0876 hours = 5.256 minutes
99.99% server uptime
Up = 364.9635 days
Down = 0.0365 days = 0.876 hours = 52.56 minutes
99.9% server uptime
Up = 364.635 days
Down = 0.365 days = 8.76 hours = 525.6 minutes
99.8% server uptime
Up = 364.27 days
Down = 0.73 days = 17.52 hours = 1051.2 minutes
99% server uptime
Up = 361.35 days
Down = 3.65 days = 87.6 hours = 5256 minutes
Initial hosting offerings of very low prices bundled with a lot of disk space and server features may be lucrative, but when it comes to server uptime, you could be paying a heavy price.
You can use other tools like ping and traceroute to measure server response times and hops required to reach your server.
