Generally-speaking, a "proxy server" is a computer (or server) that stands between your computer and your Internet service provider (ISP) "host" computer (or server) when you access the Internet. Proxies are an intermittent (albeit mostly invisible) occurrence over any connection--the only instance you'll know for sure that you're using a proxy is when you deliberately employ one to gain access to blocked websites. For example, if you live in China or Iran, you may need a "web proxy" to use Facebook. You should manage your proxy settings according to how you employ proxy servers.
Open a "Local Area Network Settings" dialog box. Open "Internet Options" from your "Tools" drop-down menu if you use Internet Explorer or Mozilla and click on the "Connections" tab. If you use Chrome, click on the "Wrench" icon, select "Options," open the "Under the Hood" tab and click "Change Proxy Settings." In all instances, click the "LAN Settings" button.
Check the box next to "Automatically Detect Settings" in the "Automatic Configuration" pane, unless you are a using a "Virtual Private Network" (VPN) that is malfunctioning. In this case, you'll want to un-check this box if it's checked--you don't want your browser to know that you're attempting to access the Internet through a (faulty) proxy. In any other instance, it's essential that your computer automatically detect proxies because your Internet connection can pass through them at any time, particularly if your ISP is a large company like Time Warner or Charter.
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Check the box next to "Use a Proxy Server for Your LAN" in the "Proxy Server" pane if you plan to employ the use of a manual proxy server. You won't need to concern yourself with this area unless someone has given you an address to type into this box.
Click "OK" to exit out of the "LAN Settings" dialog box, then close and re-open your browser so that your new proxy settings take effect.