Optify identifies key indicators from all leading search engines when attributing keyword traffic to paid campaigns. To allow us to track paid search visits and leads, customers need to turn on tracking URLs either in Google, Yahoo or Bing. These links explain the different ways to use the different parameters with these engines

Google

How do I tag: http://www.google.com/support/googleanalytics/bin/answer.py?answer=...

How does auto tagging work (gclid): http://www.google.com/support/googleanalytics/bin/answer.py?answer=...

General terms \ URL builder: http://www.google.com/support/googleanalytics/bin/answer.py?hl=en&a...

Yahoo

http://help.yahoo.com/l/us/yahoo/ysm/sps/screenref/16897.html

Bing/MSN

http://help.live.com/help.aspx?project=adcenter_live_ss&market=...

We currently assume that presence of any one of the following parameters in the above URLs indicates paid search. In particular 'OVKEY', 'YSMKEY', 'UTM_TERM', 'QUERYSTRING', 'OVRAW', 'YSMRAW', 'GCLID ', 'MSCLKID', 'YSMWA', 'UTM_SOURCE', 'UTM_ID', 'OVADID',  'YSMADID', 'OVKWID', 'YSMKWID', 'OVCAMPGID', 'YSMCAMPGID'