overflow-y: scroll;

...as a CSS style will put a vertical scrollbar on a div. overflow-x: scroll; will moreover put a horizontal scrollbar on a div. Please note that the addition of overflow-y: scroll; alone will also empower horizontal scrolling if you have a string of unbroken copy that is wider than the div itself present within the div such as, perhaps, supercalifragilisticexpialidocious.