[Nemesis]

you can only use over 70% of cpu/ram in 5 instances a day so if your getting lots of traffic and clicks/actions etc. and cpu/ram is over 70% for long periods of time it will place your site as unavailable. This is the standard for shared hosting and means its time for a vps or dedicated server. But you should be fine if you spread your sites out so the system can load balance them all.