You can look up common land on "magic mapping, here

http://www.magic.gov.uk/website/magic/viewer.htm?startTopic=magicall&chosenLayers=commIndex&xygridref=442100,84500&startscale=10000

Basically, once you get smaller scale than the Isle of Wight fill your your whole screen they don't let you see the "common land" filter any more because there isn't enough to be seen!