Not all pages allow the site to be shown in an iframe. I know you said the yahoo link is just an example, but that is one of the sites that does not work. Also, you do not need to have a ';'. I tried using bing.com (which I know works) and it loaded correctly:
Ah, I see. Did you make sure to change the & to & in the URL? Other than that, the format looks correct. Here are instructions if you weren't already aware of them: Instructions for creating CUIC Gadgets
Gadget Configuration Class finesse.gadget.Config Provides configuration data from the container page for the gadgets Config object in the Finesse desktop. When Finesse desktop load successfully, the container loads configuration details from the server. While creating gadgets, these configurations are passed to the gadgets as finesse.gadget.Config object. For more information on gadgets. Field Details Field Description authorization The Base64 encoded "id:password" that can be used for non-SSO authentication by the gadget to make Finesse REST API requests. authToken The token used for authentication in SSO deployments. clientDriftInMillis The time difference between the client and the server in milliseconds.