Block Specific Websites for Specific Users
The web filter function can help you. Do as below please:
1. Create a Web filter rule: check "Site Filter" and "Forbidden Sites" and then enter sites you want to block such as ".yahoo.;.facebook." will block yahoo and facebook. The wildcard is usually used for this function.
2. Enable Web Filter function for the accounts which you want to limit and choose the web filter rule you have created for these accounts.
For more details, please refer to Account Management.