There are reasons for web restrictions...
If you are on a LAN, your net admins have reasons for imposing these policies to the users.
Going around these restrictions probably violates the terms of your using the LAN and can subject you to all kinds of trouble. I suggest, that you consult your net admin if you need to get to a certain site. Messing with LAN policy really pisses net admins off, and especially when you catch people trying to go around policies that are there for a reason.