Will enabling auto-tagging affect the historical data accumulated for ads?
11:53 pm on Jul 11, 2012 (gmt 0)
In AdWords no, it will not affect your ad data.
All Auto-tagging does is append utm parameters to your outbound AdWords PPC URLs so that Google Analytics can properly identify it, and that just applies to what is recorded in Google Analytics, not in AdWords.
In AdWords, nothing will change. If the site uses Google Analytics, turn it on (unless you have some weird technical reason to leave it off - which would be very unusual and rare). If the site uses another Analytics platform, it is most likely built to accept and understand the tagging conventions used by Google Analytics, so also turn it on.