I can't connect to some internet sites. It says that the site can't be REACHED. I tried getting rid of the proxy server but it didn't work. A few sites work and some don't. I would try Windows Network Diagnostics that's suggested to me when the site says it can't be reached but that doesn't work for some REASON. It says an error has happened while it was troubleshooting. I don't what to do. I've unplugged the modem for 2 to 5 mins. and that doesn't work. I don't know what else to do. It can be a problem with secure CONNECTIONS. This would explain why some websites work (they use unsecure HTTP connections) and some don't (they use secure HTTPs connections).1) Click START and enter: CMD
    Right-Click on the Command Prompt Option and select "Run as administrator"   
    When the command prompt window opens type: ipconfig /flushdns    Press ENTER   
    Close the command prompt window and try the sites again   
2) If it's still an issue, see if the same thing happens with a different browserI was able to fix it. I think I just pressed the router button on my modem and it worked.