You can always block domains individually of course in your account (and whitelist them too).
I gave it a try and it looks like adblock plus gets 1st crack and then opendns domain blocking after that. See the following 4 clips to show the results:
Neither adblocking technology turned on:
Only OpenDNS domain blocking on:
Only Adblock Plus add-on turned on:
Both OpenDNS domain blocking and Adblock Plus add-on turned on:
So it looks like Firefox Adblock Plus add-on will get control 1st and if that doesn't catch it, then OpenDNS domain blocking will catch any that are missed. -- My BLOG .. .. Internet News .. .. My Web Page