SO animate CSS3 transform

HTML

<div id="foo">Text</div>

CSS

#foo {
   width:100px;
   height:100px;
   position:absolute;
   top:100px;
   left:100px; 
   border-spacing: 0;
   background-color:red;
}

JavaScript

$('#foo').animate({  borderSpacing: -90 }, {
    step: function(now,fx) {
      $(this).css('-webkit-transform','rotate('+now+'deg)'); 
      $(this).css('-moz-transform','rotate('+now+'deg)');
      $(this).css('transform','rotate('+now+'deg)');
    },
    duration:'slow'
},'linear');