The restriction was lifted during Muromachi Period (1336–1573), when a market appeared on the island and a city developed around it. But even if the island opened to public, some rules still apply: no deaths or births are allowed near the shrine, so even today, the pregnant women, the terminally ill and the very old people are supposed to go to the mainland...
Besides the main shrine, the Itsukushima complex also includes secondary shrines and all these buildings are connected through a network of amazingly beautiful roofed corridors, also built also on pillars, as you can see in this photo, taken during low tide:
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 8mm
Aperture: F/5.6
Shutter Speed: 1/320s
ISO Sensitivity: ISO 200