How can I connect to the internet when every time I try to open a page it tells me it cannot be reached because the connection was reset?

My internet was working fine yesterday, but today every time I try to open a webpage, it tells me the page cannot be reset because the connection was reset.  It tells me to check my internet connection, the proxy, and the firewall.  The internet connection is fine.  I have looked at the proxy and the firewall settings, and can't see any obvious problem, although I am not sure what exactly I should be looking for.  What do I need to do to fix this problem?  Thanks!