浮动

 

<div id="sml_box" class="club_wrap mt15 clearfix" style="height:91px;">

<div id="sml_title" class="sort_wrap">

 

 

<script type="text/javascript">

var boxHeight;

var startPos;

function startbox(div,box,classN){

         var elm = $(div);

         //classN_width = $(".classN").width();

         $(window).scroll(function(){

                   //if(!startPos){

                            startPos=$(box).offset().top;

                   //}

                   var p = $(window).scrollTop();

                   if (startPos < p)

                     {

                              $(elm).addClass(classN);

                     }

                   else

                     {

                              $(elm).removeClass(classN);

                     }                        

         });              

}

startbox('#sml_title','#sml_box','twfir');

</script>