This is checked from your Firewall logs or content filter. Is this for your job site? I use barracuda firewall+content filtering where I work, which allows me to view logs, statistics, sites visited, etc..... It all depends on the type of hardware you have. If your talking about logs from a router, unless it's supported and enabled, I doubt it will hold any info, unless it's configured to do so (log data retention). You could perform packet sniffing and other advance features, but those can be (sometimes) frowned upon. I'll leave it to you to research those features.