Popups can be a good way to show meta-information or to confirm an action. Unexpected pop-ups are pretty annoying and making them hard to close will make your users mad. Pressing the close icon or cancel button should not be the only way to close a popup.

Take this action

Make the clickable area of the close icon at least 40 x 40 pixels and hide popups when the user clicks on the background or presses the escape key.