Plly, ignore the pr*ts who have answered already. You need to provide more information before anyone can answer correctly. Hos have the sites been blocked? is it by your own Firewall or a company/school/other firewall? if it is your own you can look in the Firewall's "blocked site" list and there should be a way of allowing them to be shown. If it is not your own firewall you should have a procedure available to request blacked sites to be unblocked if you have a good reason to access them.
Russell Taylor, December 2007