First try to ping a website(for example www.google.com) from your console->ping www.google.com to see if your internet connection is really working.

You could also try to configure your proxy. Many corporate networks rely on SOCKS proxy servers for access to the internet. Typically a Proxy Auto Configuration (PAC) script is issued to be registered with the browser. These scripts are usually targeted to Microsoft Explorer of Netscape Navigator (4.x) specifically. Try the proxy script: "Edit" + "Preferences" and select "Advanced (+)" and "Proxies" + "Automatic proxy configuration URL", enter the script location and select the "Reload" button.

If it works, great your ready to surf. If your corporation uses a proxy directly, enter it under "Manual proxy configuration". If using a script and it does not work, use the command "wget http://proxy-url.domain.com/proxy-script.pac" to download the proxy script. Examine the file proxy-script.pac.
Burried in the logic of the script is usually the explicit listing of a proxy server which can be entered under the Mozilla manual configuration. If you are at a corporation using a firewall and have direct access,you have no need for proxy configuration.

Source: yolinux.com