Squid/proxy expert

I have Squid installed on my (external ) WEBSERVER, and want visitors of my site to be able to connect to certain sites trough the squid proxy. This should preferably work without the customer needing to adjust proxy settings in his/her browser. Im not sure if its possibe to link trough the proxy without changing browser settings (?) Other things i would like to have configured: - i have a whitelist of about 10 sites where i want to allow my visitors to connect trough via squid. All other sites should be blocked. - I only want actual visitors of my site to be able to connect trough the proxy