What do you mean by "web key"? There are several passwords on a typical router such as the internet connection password, the wi-fi password and the router control panel/web interface password.
If you mean the WEP Key and not the web key you can find it following these steps.
Go to the computer's wireless networking setup screen and see if you can detect your router's SSID. Select that network. Apply the wireless security type and password to the computer's wireless networking setup screen.
P.S: If there is no response from the router the default address may have been changed.