Some countries or ISP have their access rules for their people to access the internet. Like China’s government that block Facebook in their country for any reasons. Then some website only accessible from some country, but mostly allowed US. But you need the information from that website, so to bypass all that filters or access rules, you can use web proxy.
What is web proxy? Web proxy (proxy server that focus on WWW request only), is a server (a computer system or an application program) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server.
Update: I moved this service to http://ivankrisproxyserver.appspot.com/. Thanks.