jquery mouseover 事件的问题

repeat -x
没有空格
$(document).ready(function(){
  $("button").mouseover(function(){
    $(this).css("background","url(http://img0.bdstatic.com/img/image/shouye/zxzzyyh.jpg) repeat-x");
  });
  $("button").mouseout(function(){
    $(this).css("background","url(http://img0.bdstatic.com/img/image/shouye/sjwysji11.jpg) repeat-x");
  });
});