I know that Symantec does not sell a spell checker in addition to their security products, but this advertisement I found on the Cult of Mac blog is still unprofessional. Then again, perhaps it is not surprising, since Norton Antivirus 2006 is not even available for Mac OS X. For protection against Mac viruses, you need Norton Antivirus 10.0 for Macintosh.
While the ads on the Cult of Mac website seem to be driven by FeedBurner (and therefore most likely not controlled by Symantec itself) and seem to be context-based (the entry beneath the ad talks about Microsoft's use of a PowerBook in a stock photo on their Security website, there is still no reason for the misspelling.
Alas, misspelling the word "safeguard" appears to be de rigueur at Symantec.