Gathering Web Activity Logs

Hi,

We recently took on a FortiGate 100E after being told we could review historical web activity. For example if it was found out someone in our company was accessing websites they shouldn't be looking at, we could review historical logs to see how long they had been doing it for and anything else. However, this does not actually seem to be the case.

Does anyone know of a service that could easily log all web activity that goes through my FortiGate, whether it's wired or Wi-Fi?

Many thanks, apologies if this is the wrong forum to post it on, wasn't sure.