Omit pop-ups from the screenshot
The first option, Omit pop-ups from the screenshot, will attempt to detect and remove the pop-up from the screenshot. This works in most cases and should be tried first. However, there are times when we are unable to detect and remove a pop-up, in these cases the second option should be used.
Omit specific elements from the screenshot
The second option, Omit specific elements from the screenshot, should be used when the first option is unable to detect and remove the pop-up. Enter the CSS selectors for the elements you’d like removed from the screenshot. For example, you can enter #pop-up, #pop-up-modal and this will remove the elements with matching selectors.
Additional information Information about CSS Selectors is available on the Mozilla Developer Network: https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Getting_started/Selectors