Dozens of pop-up ads cover a desktop.

Pop-up ads are a form of online advertising on the World Wide Web intended to increase web traffic or capture email addresses. It works when certain web sites open a new web browser window to display advertisements. The pop-up window containing an advertisement is usually generated by JavaScript, but can be generated by other means as well. A less intrusive variation on the pop-up window is the pop-under advertisement. This opens a new browser window, but in the background, so as not to interrupt the user's page-view.

For early advertising-supported web sites, banner ads were sufficient revenue generators, but in the wake of the dot com crash, prices paid for banner advertising clickthroughs decreased and many vendors began to investigate more effective advertising methods. Pop-up ads by their nature are difficult to ignore or overlook, and are claimed to be more effective than static banner ads. Pop-ups have a much higher click rate than web banner ads do.

Most users regard pop-ups as a nuisance. In the early 2000s, all major web browsers except Internet Explorer (then the most popular browser and still as of 2004) allowed the user to block unwanted pop-ups almost completely. In 2004, Microsoft released Windows XP SP2, which added pop-up blocking to Internet Explorer. Many users, however, remain unaware of this ability, or else choose not to use it. Some users install non-Microsoft ad-blocking software instead. Advertisers continually seek ways to circumvent such restrictions. Many of the latest pop-ups are created using Flash and have extensive animation and trickery.

Pop-up ads can also be spawned as a separate process (that is to say, apart from the browser) on the user's local computer. This is typically because of a spyware infestation, or because the user has voluntarily (or involuntarily) installed adware.

A particularly common type of pop-up ad exploits the Messenger service in Microsoft's Windows XP operating system. Claims have been made that this type of pop-up has been used to commit extortion. Threats of legal action against the company D Squared Solutions has caused them to stop using this technique.

Pornographic web sites are among the most common users of pop-up ads. Some particularly vicious types of pop-up ads (again, most often seen in connection with adult entertainment sites) appear to have either been programmed improperly or have been specifically designed to "hijack" a user's Internet session. These forms of pop-ups sometimes spawn multiple windows, and as each window is closed by the user it activates code that spawns another window -- sometimes indefinitely. This is sometimes referred to by users as a "Java trap", "spam cascade" or "Pop-up Hell" among other names. Usually the only way to stop this is to close the browser.

Another variation of pop-up, commonly called "mousetrapping", particularly fills an entire screen with an ad or Web page, in the process removing any menu bars or other on-screen icons by which the user can close the window. This problem mainly affects users of the Windows version of Internet Explorer. Often, access to other open windows and Web pages is denied and the only way for PC users to close these ad windows is via the control-alt-delete command, which can result in all active IE windows (including those not connected to the pop-up) closing. Another way to close the mousetrapping window could be to hold down the Alt button and press F4. This closes the active window.

Browsers that block pop-up ads

• Gecko-based browsers
  • Mozilla
  • Mozilla Firefox
  • Netscape 7
  • Camino
  • Galeon
  • Epiphany
• Internet Explorer (if Windows XP SP2 is installed)
• Opera
• Safari
• America Online 9.0
• Konqueror

Add-on programs that block pop-up ads

• Google's Google Toolbar
• KillAd -- freeware
• NoAds -- freeware
• Pop-up Stopper
• Proxomitron
• Popup Blocker by Osborn Technologies http://www.osborntech.com/pub.htm -- An unobtrusive freeware popup blocker for Internet Explorer
• MSN Toolbar
• Bayden Systems Popup Blocker

See Also

• Computer virus
• Junkmail
• Malware
• Static image ad

External links

• BannerReport.com - The Internet Advertising Resource Guide - includes a searchable gallery of 15 000+ banner ads
• ASAP! - A Stand Against Pop-unders
• Pop-up Test - a site for testing how well your pop-up blocking software works
• Free Pop Up Blocker - lists several free pop up blocker add-ons
• How to Find, Remove and Prevent Spyware, Internet Intruders, and Pop-Ups
• What's up with popup ads? (from The Straight Dope)
• SurferBeware.com Popup Ad Help — Everything you ever wanted to know about popups, including how they are created, what makes them tick, and most important how to stop them.