A pop-up page is any page that causes the browser to display the page content in a new browser window. During a visitor's session, the visitor usually closes this window and then proceeds to click a link or button that is found on the page that is displayed in the original window.

In RTV, pop-up windows interrupt the flow of displayed visitor impressions. Unless RTV is provided information that identifies a page as a pop-up, RTV cannot correctly show the data that is entered by the user on the page's input fields. When a page is requested, RTV examines the field names of the immediately preceding page in the session sequence to identify the matching field names. When a pop-up page is present, the pop-up is part of the sequence, yet RTV fails to find matching field names in it. Therefore, RTV does not know where to display the data.

The referrer of the second full page is the first full page, with the pop-up page displayed in between. While RTV recognizes that the pop-up occurred between the full pages, RTV assumes that the visitor clicked the Back button in the web browser to move back to the first full page before the visitor moved on to the second full page. However, it is more likely the visitor closed the pop-up window and then clicked a link to proceed to the second page.

Pop-ups also affect detection of presses of the browser's Back button. RTV relies on the HTTP_REFERER information for Back button detection.

RTV uses HTTP_REFERER to match a page with its form field and to highlight information, thus reducing or eliminating the need for a profile to identify pop-up pages.