How do I unblock a website?

I tried going on a website on my laptop but instead it went to a page saying: "Access to the web page you were trying to visit has been blocked in accordance with company policy. Please contact your system administrator if you believe this is in error." I don't understand why it would do this all of a sudden. I was on the website earlier in the day and it worked fine. Also, I'm the system administrator and I didn't change any of the settings on my computer or block them. I'm really confused and don't know how to unblock them