easyui弹出对话框在更改宽度时位置出现偏移

 easyui弹出对话框在更改宽度时位置出现偏移
 <%@ page language="java" contentType="text/html; charset=utf-8"
     pageEncoding="utf-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 <title>Insert title here</title>
   <script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-1.7.2.min.js"></script>                                                           
   <script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery.easyui.min.js"></script> 
   <link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/themes/default/easyui.css">   <!--引入CSS样式-->
   <link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/themes/icon.css">   <!--Icon引入--> 
   <script type="text/javascript" src="${pageContext.request.contextPath}/locale/easyui-lang-zh_CN.js"></script>  <!--汉化-->
        <script type="text/javascript">
            $(function(){
                $("#d1").dialog({
                    title:"fdfd",
                    width:200,
                    height:300,
                    collapsible:true,
                 buttons:[{text:"确定",handler:function(){
                                //begin
                    $("#d1").panel({width:900});
                                    // $("#d1").dialog({width:900});当使用这个时不会,为什么
                                    //end
                     $.messager.alert("你点击了确定将立即进行宽度的更改");


                 }},{text:"取消",handler:function(){
                     $.messager.alert("你点击了取消");

                 }}]

                });
            });
        </script>
 </head>
 <body> 
 <div id="d1"></div>
 </body>
 我是新手,麻烦用通俗易懂的话语告诉我,谢谢