diff --git a/app/views/courses/_course_ad.html.erb b/app/views/courses/_course_ad.html.erb
index f8b4781f8..efac79afc 100644
--- a/app/views/courses/_course_ad.html.erb
+++ b/app/views/courses/_course_ad.html.erb
@@ -33,12 +33,11 @@
     var xstep=1;			// 移动步长，此参数越小，移动越平滑，最小值为1
     var delay_time=60;		// 每步的时间间隔，此参数越小，移动速度越快
     var YY=0;
-    var screen_height = $(window).height();          //浏览器当前窗口文档的高度
-    var screen_width = $(window).width();            //浏览器当前窗口文档的宽度
 
    window.setInterval(function(){move();},delay_time);
    function move()
    {
+       var screen_height = $(window).height();          //浏览器当前窗口文档的高度
        var floatpoint_height = $("#floatpoint").height();
        YY += xstep;
        if(YY <= 0){xstep = 1; YY = 0;}					//如果浮动层超出了上界，则设定移动方向为向下；并设定层的位置为正好在上界处
@@ -47,9 +46,9 @@
            xstep = -1;
            YY=(screen_height-floatpoint_height);
        }
-       $("#floatpoint").css("top",YY);
+       $("#floatpoint").css("margin-top",YY);
    }
-   function change_size(){var body_width = $("#top-menu").width(); $("#floatpoint").css("left",screen_width/2+body_width/2+10);}
+   function change_size(){var screen_width = $(window).width();var body_width = $("#top-menu").width(); $("#floatpoint").css("left",screen_width/2+body_width/2+10).css("position", "fixed");}
    $(document).ready(function(){change_size();});
-   $(window).resize(function(){screen_width = $(window).width();change_size();});
+   $(window).resize(function(){change_size();});
 </script>
\ No newline at end of file