Help Desk
By Jack Szwergold, Guest Webmaster
Use Your Middle Man
Dear Help Desk,
I was confused by one of the points made in the article entitled "None of Your E-Business" in the April 2000 issue of Web Techniques. In this article, an HTML segment is referenced as follows:
<img src="http://doubleclick.com/images/nike-shoes.jpg">
and indicates that when DoubleClick serves the page, it also includes a cookie in the response.
Earlier in the article the author states that the page is on site A. I'm interested in knowing how a cookie can be set by serving up an image from DoubleClick's site.
—T. Allen
Dear T.,
Banner ad delivery is tricky. Delivery coupled with cookie tracking is even trickier. While DoubleClick does indeed serve the graphic, DoubleClick cannot set a cookie by simply serving a graphic in the traditional, hard-coded URL sense. Nobody can. But, with the help of a "go between" script or ad server, ad delivery companies like DoubleClick—and others—can serve your banner and give you a cookie, too. Here's a glimpse at how this works.
Say you're surfing www.theonion.com (shameless plug) and a banner ad from DoubleClick pops up. If you take a look at the source code, you won't see a clean hard-coded URL like:
<IMG SRC="http://doubleclick.com/images/nike-shoes.jpg">
Instead, you'll see an odd-looking URL—a call to DoubleClick's ad servers—that looks something like this:
<IMG SRC="http://doubleclick.c
