What browser are you using? Have you tried a different one? Exactly what happens when you try to type something into your search engine?
Google Chrome, Google, Safari, MS Explorer. We either get nothing just site processing, or site not available response
Check your Safe Browsing settings in Chrome.
I'm having the same problem, but only on one laptop. Others appear fine and it appears comcast is protecting me from myself. No access to almost any site except for Facebook and a few others. No eBay, amazon etc