Popup ads

Pop-up ads or pop-ups are forms of online advertising on the World Wide Web. Pop-ups are generally new web browser windows to display advertisements. The pop-up window containing an advertisement is usually generated by JavaScript that uses cross-site scripting (XSS), sometimes with a secondary payload that uses Adobe Flash. They can also be generated by other vulnerabilities/security holes in browser security.

A variation on the pop-up window, the pop-under advertisement, opens a new browser window under the active window. Pop-unders do not interrupt the user immediately, but appear when the user closes the covering window, making it more difficult to determine which web site created them.

Pop-up ads originated on the Tripod.com webpage hosting site in the late 1990s. Ethan Zuckerman claims he wrote the code to launch advertisements in separate windows as a response to complaints of displaced banner ads. He didn't invent the pop-up window. Zuckerman later apologized for the unforeseen nuisance pop-up ads had evolved into.

Opera was the first major browser to incorporate tools to block pop-up ads; the Mozilla browser later improved on this by blocking only pop-ups generated as the page loads. In the early 2000s, all major web browsers except Internet Explorer let users block unwanted pop-ups almost completely. In 2004, Microsoft released Windows XP SP2, which added pop-up blocking to Internet Explorer. Most modern browsers provide pop-up blocking tools; third-party tools add other features, such as ad filtering.

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