Pop-Up Ad: Pop-up ads are type of online ads, where a new web browser window is opened to display advertisements. Using JavaScript, ads are launched in new browser while a web site is being viewed. Sometimes pop-up ads may be pornographic, games-related and unnecessary annoying ads. Because of it’s widespread, users tent to close the pop-up advertisements without looking at them.
Pop-Under Ad: In contrast to Pop-up ads, pop-under ads will appear behind the browser window of a Web site that a user has visited. pop-under ads will hide behind your browser until the main browser window is closed. Pop-under windows are less intrusive than the pop-up windows, so pop-under advertising is more effective compared to Pop-up ads and becoming increasing popular with advertisers.
Recent reports shows that Internet marketers are using Pop-under ads as an effective alternative to the declining banner ads.