From the website:

The government says it is unable to connect to the giant undersea fibre-optic cables because of the US trade embargo. All online connections today are via satellite which has limited bandwidth and is expensive to use.

Cuba's anti-American ally, Venezuela's President Hugo Chavez, is laying a new cable under the Caribbean.

It remains unclear whether, once the connection is completed, the authorities will then allow unrestricted access to the world wide web.