Our facebook , youtube and friendster were blocked..how can we unblocked this one???

What ever the site you are unable to open add it to the Trusted sites and remove it from the restricted sites. You may want to do by following the steps below,

Step 1: Click on Tools....Internet Options.
Step 2: Click on the Tab Called security.
Step 3: Left click once on Restricted sites then click on a Tab called site.
Step 4: Check for any sites listed in the box there if you find the one you wanted then select it and remove.
Step 5: Click apply and ok. Relaunch IE

Follow Step1 and Step2 (For Adding)

Step 3: Left click once on Trusted Sites then click on a Tab called site.
Step 4: Type the URL u want to access then click on add.
Step 5: Click apply and ok. Relaunch IE