From the jQuery docs:
Setting the value of a style property to an empty string — e.g.
$('#mydiv').css('color', '')— removes that property from an element if it has already been directly applied, whether in the HTML style attribute, through jQuery’s.css()method, or through direct DOM manipulation of thestyleproperty. It does not, however, remove a style that has been applied with a CSS rule in a stylesheet or<style>element.