Website displayed within iframe from google maps link

Hi, i have a problem that is driving me crazy!!!

i have a google map embedded on my page. When clicking on a marker on the map and then clicking the “more” link, the page seems to load with the whole website within the google maps iframe!

link to site – http://heritage-is.org.uk/map/

Any ideas ors thoughts on how to resolve would be greatly appreciated.

Thanks

mogito