The -moz-border-radius-topleft Mozilla extension property is used in CSS and certain HTML elements to create a rounded border on the top left corner of a particular object. The -moz- prefix specifies that its effect can only be seen in browsers which use Gecko as their web engine, like Mozilla Firefox, as moz stands for Mozilla. It will only create a border if there is a specific background-color/image on the object. For functionality on other browsers, use the border-radius property. To specify a border radius to the other individual corners, use the