You want to know what classification to use for a certain URL
You can not effectively block a site unless you choose the correct classification of the URL.
In SWG, there is a tool to find the classification of URL. You can find the URL by navigating to the SWG interface.
1. Administration > Configuration > Modules > Click on "Request changes to Content Filter classification"
2. A new page will open, then enter the URL (ie. yahoo.com) and click "send" button.
3. This will result with a list of categories for that site, which you can then use for your policy.
Outside the SWG interface you can query directly the website: