Following the excellent guide on Adafruits website I've added a DNS server / add blocking setup to my Bitorrent Sync Raspberry Pi 5. This blocks any requests for banner advertising so when browsing to certain websites they are advert free. This will also work on Playstations, Xbox's, tablets and mobile phones when connected to my local wifi.
Before and After shots of the same web page below. The colour change is part of the advert on the left.
Only change to the guide is I had to run the following command at the start
sudo apt-get update
I also changed by routers Default DNS from my ISP to my Raspberry Pi's P address.
Unfortunately it doesn't look like the scripts for removing sites from the list is working. If you use quidco etc you might have to change your PC's DNS server manually to 18.104.22.168 (Googles open DNS servers)