This can be because either it is the old version of the website stored in the browser cache, this can usually be cleaned out by pressing Ctrl + R (PC) or Cmd + R (Mac).
If not, it may be that you recently made a name server change, then it may take up to 48 hours before you see your website fully.
It may be that you need to clear out the DNS cache on your computer. This is done with the following commands:
Windows: type ipconfig / flushdns at a command prompt (run as administrator if you have Vista or Windows 7)
Mac: open a terminal and type in dscacheutil -flushcache and hit enter, followed by lookupd -flushcache
Linux: Open a terminal and type /etc/init.d/nscd restart
Then start the browser again.