Pops creatives are shown to users in a variety of ways, and the dimensions of your creative can vary.
Depending on the traffic channel that served the impression, your creative may be shown any number of ways. Most Pops impressions will open your creative in a new tab to the right of the user's current tab, with the new tab taking focus.
Pops impressions are also served on mobile devices and tablets. The way your creative is shown to mobile and tablet traffic varies by channel and also depends whether the impression is served on a browser or an app.
TIP: Your landing page will be sized differently depending on the user's device, screen resolution, etc. Users can also drag the edges of the browser window to resize your page on their screen to any height and width. Using responsive design on your landing page is a best practice to ensure your page looks best for every impression.