<div id="up">xxxxx</div>
 <div id="down"></div>

  function showorhide(){
      // 显示
      if($("#up").is(":hidden")){
          $("#up").show("slow",function(){
            $("#down").css("height",all-$("up").height());
         });
      }else{
          $("#up").hide("slow",function(){
            $("#down").css("height",all+$("up").height());
         })
     }
  }