If your router don’t have Content Filtering Feature, then you can also block a website using hosts file of your Windows OS: http://www.dailytechtuts.com/240/block-website-in-windows/
In this video we will see How to Block ANY Website or a Specific Keyword using the in-built Firewall/Content Filtering feature present in your Wi-Fi Router?
I am using NETGEAR Wi-Fi Router, but if you are using a Router of some other Manufacturer like Cisco (Linksys), D-Link, Belkin, Apple etc., then check your Router’s offline/online manual. I am sure Content Filtering Feature must be present in it.
Content Filtering Feature present in a router helps in:
* Blocking access to certain domains (for example, www.badstuff.com/XXX)
* Blocking sites that contain certain words related to profanity or explicit sexual material.
Either you can block ANY Website or a Keyword permanently on your Home/Office Wi-Fi Network OR you can set a specific schedule for the blockage.