Well it depends on what browser you are using.  If you are using internet explorer the simplest way it to hit the history button, but they most likely deleted those files.  You could download a program that takes screen snapshots and saves them to a folder or you could use a bandwidth monitoring program like PRTG Traffic Grapher, but that is a little more complicated and not ideal for what you want, but it will give you a general idea.  Do a internet search for tracking web activity or something like that.