Yes I believe firewall can and will do that, it's call filtering webpages base on content. Depending on how high you set the firewall filtering level to, it will filter out most webpages that fit the description. And yes it can still be view if you set the level lower or turn it off. If you are using IE, check your internet option. If you're behind a router in a workplace or school, there is a reason why they don't let you go on certain pages but there are ways around that.