There are ways (mouse or keyboard) of overriding cached versions, either local ones or further down the line at your ISP, but without knowing which operating system and browser is being used, it's hard to give any dependable pointers.
Typically, across platforms, Windows, Mac, Linux, just clicking the Refresh icon in a browser or pressing the F5 key performs a simple refresh, but if you want to override caching, you can hold down the Shift or Ctrl key while clicking Refresh or else hold down the Ctrl key (Cmd on a Mac) and press F5.
Pretty comprehensive guide here:
http://en.wikipedia.org/wiki/Wikipedia:Bypass_your_cache