An alternative is to simply add the specific campaign information to the URL of the click, for example if you are sending clicks to http://www.MySiteTraffic.com for a keyword bidding campaign for "TRAFFIC", you can simply append the string to the click URL http://www.MySiteTraffic.com?bidkeyword=traffic
This allows you to do a FIND for "bidkeyword" and find the traffic that arrived at this URL. Since this URL string is only used for this campaign, it is easy to find the visitors that arrived at your website as a result of this campaign.

You can do further analysis for each session that you identify from your campaigns, such as viewing their click-path through your website. This will allow you to determine if the visitors found what they were looking for (and if they reached the purchase page).

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