You seek to determine which URL Filtering categories a particular website is in whilst preparing for building your SWG filtering policies.
Symantec Web Gateway (SWG) 4.5.x and 5.0 uses the Cobion URL Filtering ruleset. You can identify category membership of any given website by looking it up at the following location: http://filterdb.iss.net/urlcheck/
The site also allows for feedback if a certain URL is believed to be wrongly categorized by using the Add and Remove buttons and sending the update. The suggestion will be reviewed and eventually implemented if found correct.