you can chain several proxies together- proxy.name.com:8080/proxy2.name.com with the name of the port for the second proxy in the port column (do not forget, proxies are not WWW servers). you can put the proxies either in the address/URL field of your browser- proxy.name.com:8080/www.URL.you.want.to.visit or inside where manual proxy config is

Maybe that helps,chaoz