My mac will not connect to the internet?

I downloaded an update about a week ago and have not been able to connect to the internet since. I Have tried several things to get it working again but it still will not work. My Macbook pro has a connection but when i open safari or firefox they will not bring up any webpages. I have run diagnostics and it says my connection is fine. Every other device in my house, (Ipod, Xbox, PC) all work fine. Any help would be great thank you ahead of time.