Use SSH server as a proxy to access a restricted web site

Step 1:
In PuTTY create a new session to connect to the SSH server which has the access to the restricted web site:
1. Go to Connection->SSH->Tunnels
2. Fill in the Source port e.g. 8888
3. Select option: Dynamic
4. Click on the Add button to add the forwarded port.
5. Save the session.

Step 2:
Use PuTTY to open a connection to the SSH server with the new session.

Step 3:
In Firefox:
1. Go to Tools->Options
2. Scroll to the end or search "Proxy".
3. Click on the Settings button for Network Proxy.
4. In the Connection Setting, select Manual proxy configuration
5. Fill in the proxy with the port we set earlier (e.g. 8888):
    SOCKS Host: 127.0.0.1
    Port: 8888
6. Click on OK to save the changes

Firefox will send all the traffic through the SSH server. Remember to change it back after use.

Now you can access the restricted web site with Firefox.