Blocked sites still accessible?

[#1]

Hi
I've got the T582n router and when I've added a certain site to block, other users can still access it. The strange thing is, it's only blocked on the device where I originally did the set-up from 
Any help ?
Thanks.

[#2]

Odd, not one I've heard of before. Have you looked at using Safeguard instead and see if that helps? https://www.plus.net/home-broadband/safeguard/

[#3]

What DNS servers are specified in the network settings of the devices that can access the sites?  Are they all set to use the router as the DNS server or are they perhaps set to use something else, such as Google or OpenDNS?

[#4]

Quote from: Chris

Have you looked at using Safeguard instead and see if that helps? https://www.plus.net/home-broadband/safeguard/

Thanks. I'll use that as you've suggested.

Quote from: pwatson

What DNS servers are specified in the network settings of the devices that can access the sites?  Are they all set to use the router as the DNS server or are they perhaps set to use something else, such as Google or OpenDNS?

All devices are using the router to access the 'net.