Web Development Insight

A web beacon is also known as a web bug, pixel tag, or a clear GIF.
Used in combination with cookies, a web beacon is an often-transparent (i.e. hidden) graphic image, usually the size of 1 pixel x 1 pixel, that is placed on a Web site or in an e-mail that is used to monitor the behavior of the user visiting the Web site or sending the email. When the HTML code for the web beacon points to a site to retrieve the image, at the same time it can pass along information:

• The IP address of the computer that retrieved the image
• The time the web beacon was viewed
• How long the page was viewed
• The type of browser that retrieved the image
• Previously set cookie values.

Web beacons are typically used by a third-party, such as a marketing firm, to monitor the activity of a site. A web beacon can be detected by viewing the source code of a web page and looking for any IMG tags that load from a different server than the rest of the site.

<img src="http://www.trackingfirm.com" />

Turning off the browser’s cookies will prevent web beacons from tracking the user’s activity but will still account for an anonymous visit. Several vendors, such as Google and Amazon, use this method for tracking.
Doug