It's easy to add Norton safe web service to Opera browser, all you need is add a new search engine like that:
At the search toolbar (where google us located) select Manage Search Engines...
Click add.
Name: Norton
Keyword: n
Address: http://safeweb.norton.com/report/show?url=%s
This is it!
Go on click ok, now type in the address bar: n site-we-check.com