lucy24 - 10:13 pm on Nov 6, 2012 (gmt 0)

I'm missing something. Why can't the javascript go straight from the click event to a function that sets the cookie? What's the extra window for? Last time I tracked clicks, I used innerHTML and a 1x1 pix dot-- but that was on a site that happened to have blank space, so the user wouldn't see a change.

Will it be the advertiser's cookie or yours? This may be the most important question, because a lot of browsers default to accepting cookies only from the site they're currently on. No third-party cookies.