Probably the most likely problem you are having now is that the proxy that you are using is blocking cookies between you and the site so the sites (Antionline.com and Yahoo.com) let you log in and then when you try to navigate from there it 'forgets' that you are logged in because it does not have the cookies from your browser telling the sites your user information. If you simply want to use a proxy for WWW surfing you can find a short list of good ones at http://void.ru (even though its in Russian the proxies are in the top right in the format of IP:Port) you can use these to copy/paste into your browser's connection tab under proxy.

[edit]
I forgot to mention before that most of these proxies are taken off of the site after about a day so to ensure that you have a good one (fast and secure) check back daily and change the IP/Port in your proxy settings.
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However if any of this is wrong I'm not perfect so please correct me if I'm wrong.