Well, surprisingly, this happens to a lot of people. Look at it like it's a good thing... but yeah, you should probably get a better hosting server.
Haha I'm being sarcastic. It is a good thing. Did my host shut down my site? Because it's on a shared server and only that one is blocked.
You probably exceeded bandwith or processor time. If its a CMS you could optimize the site by using fewer images or an addon that will cache pages. If its bandwith, you just need a better host.
There are a lot of things that could have happened to your hosting account, given that it's shared. Your host could have limited your CPU usage, you may have reached your bandwidth limit, the connection's upload speed may not be sufficient, or your other vital server components (RAM, /tmp, etc) may be maxed out. Depending on whether you are getting an error message, a timeout, or a connection error, you should be able to determine what the problem is. If it matters to you, file a support ticket or call your host for help. Any decent host should be willing to help you out in a situation like this (traffic slam) in a timely manner. You should consider upgrading to a dedicated server or VPS in the future, so you don't have this problem again. Also, a dedicated server with root SSH or cPanel WHM accessibility allows you to access the advanced features of the server in times of need (as you can almost always connect to the server even if HTTP is down). Shutting down unnecessary services, enabling caching, and resetting the server altogether can all help reduce load and bring the sites back up, at least temporarily. Good luck next time.