Go to Source
From time to time you might see a “not set” entry in your Top Content or Keywords reports. Hopefully at this point you go to the Google Analytics Help Center to do a search for “not set” to find the definition. 
If you don’t, not to worry – this blog post sums up why this entry appears in your report and what you can do to prevent it from happening in the future.
“not set”
Any direct visit or referral visit will be shown under “not set” because it does not have a keyword, ad content, or any other campaign information associated with the visit. The explanations below can help you figure out why a campaign attribute wasn’t collected along with the visit.
Re-tagging your AdWords destination URLs
If you are seeing a significant amount of “not set” or ‘(not set)’ entries in your AdWords-related reports, you may wish to disable auto-tagging and instead use the URL Builder to tag your destination URLs so that they’re set to the specific campaign variables you want to appear in your reports.
gclid redirection for keywords
Sometimes Analytics users are master URL taggers and still see a “not set” keyword entry. Usually this happens when there is some kind of redirection and the gclid (which is the magic that makes autotagging happen) doesn’t work the way it’s supposed to. At this point, we recommend you do some detective work going backwards from what you know. Start by clicking on the “not set” entry, and from the Dimension menu, select ‘Source’ and then ‘Medium.’ You can also select ‘Landing Page’ in the Dimension menu if ‘Source’ or ‘Medium’ doesn’t give you any clues about the missing keyword. These segmenting options should help you narrow down the source of this keyword so that you can pinpoint which keyword’s gclid isn’t behaving properly.
For more information, search the Google Analytics Help Center (it’s important to include the quotation marks!) by entering “not set” in the search box. If you know of any other tips or tricks about “not set” entries, please feel free to post a comment.
Posted by Christina Park, Google Analytics Team
