http://api.jquery.com/css/#css2: Shorthand properties

[timmywil]

We state that shorthand properties such as border and background are not supported in the getter. While setting these properties works fine with most values, resetting does not. When setting shorthand properties to empty string in IE, they are nullified and previous styles are lost.

e.g.

$elem.css({
  "background": "",
  "border": ""
});

[staabm]

see also http://bugs.jquery.com/ticket/12385