Found on all three of my browsers (Chrome, Firefox, & IE): StartNow. When I removed/disabled this extension/add-on, the coupon popups all disappeared.
I have a related observation. In addition to the popups, my outgoing emails would have links inserted randomly into the text, apparently as they were sent. I noticed it when the friend that referred me to this site replied with the thread intact:
I did not save the link but just checked it again now and it no longer links so it appears this was also something being done by the StartNow program.
Edited by JCwrite, 27 November 2012 - 10:46 AM.