Having your proxy settings tampered with is a common side-effect of viruses. Some viruses set proxy servers within the browser settings so the browser will reroute its connection through a made-up server. This blocks you from getting on the internet to download virus protection software, among other issues. When you experience a bad proxy server entered into your browser, it will show up as a connection error within the browser.
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Go to Tools -> Internet Options.
Click the Connections tab.
Click LAN settings in the lower right of the pop-up window.
Check to make sure the option for Automatically detect settings is checked and NOTHING is checked in the Proxy Server section.
If there is something checked in the "proxy" portion of that window, remove the check mark checkmark and make sure the Automatically detect settings box is checked above.
Click OK.
Click Apply if any changes were made or OK to exit the window.
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Reboot your computer. If you still cannot access the internet, check your network connection. If necessary, contact your desk side support or take your computer to an ITS Service Center.