Some websites, like facebook, youtube, are rather time consumable.
If you do nothing to filter certain websites, your employees may spend several hours a day on web surfing.
So How to block certain websites to save your productivity?
1. Some router/gateway might have the ability to block certain websites.
2. Firewall appliances, like cisco PIX, will also be a good choice.
3. The third, you can choose internet filtering software to do web filter and blocking.
Most employees waste more than an hour on browsing web pages. Even worse, someone will not be able to concentrate on their work during work time.
So, to save productivity, it is necessary for organizations to block certain websites and restrict internet access.
In my opinion, things should be done from several aspects:
1. Only work-related websites are allowed during work time.
2. Destructive websites like violence, adult, shall be blocked always.
3. Downloading websites shall be blocked to save bandwidth if you are suffering from slow internet speed.
For those companies who are very strict with websites browsing, you can implement a website whitelist, by which, only websites in the whitelist can be visited.
More information, please refer to internet blocking and internet monitoring.