Is an ad that opens in a new browser window that pops up while browsing a web site. These windows may pop-up when you first visit the site or when you leave the site.

Pop up windows come in many different shapes and sizes, typically in a scaled-down copy of your browser window. Many internet users find pop-ups annoying and have them blocked using the browsers pop-up blocker or 3rd party software to block the pop-up ad’s

Many website owners user their own programming (javascript) to server the pop-up ads on their sites. There are also many pop-up networks that just server the pop-up ads.

Pop-Up ads are many used to generate revenue for the site owner but many are used as subscription forms to newsletters.