masterpage menubar childnode going behind the Ajax page

Question

sir my CSS Code is below ::

   <style Style="z-index:1000">

        *

{

      margin : 0px;

      padding: 0px;    

      }

      body

      {

            font-family:Verdana;

            background-color:#ABC;

            padding:0px;           

            }

            h1

            {

                  text-align:center;

                  border-bottom:2px solid;

                  margin-bottom:50px;

            }

            /* rules for navigation menu*/

            ul#navmenu, ul.sub1, ul.sub2

            {

                  list-style-type : none;

                  /* border:1px solid red;*/

                                   

                  }

                  ul#navmenu li

            {

                /*border:1px solid red;   */               

                width: 125px;            

                text-align:center;

                position: relative;

                float:left;

                margin-right : 4px;

            top: 0px;

            left: 0px;

            font-size: small;

            font-weight: 700;

        }

            ul#navmenu a

            {

                text-decoration : none;

                  display:block;

                  width : 125px;

                  height: 25px;

                  line-height:25px;

                  background-color :#FFF;

                  border:1px solid #CCC;

            font-size: small;

        }

            ul#navmenu .sub1 li

            {

                  /*    border : 1px solid green;*/

                  margin-top : 5px;

            }                            

      ul#navmenu .sub1 a

      {

            margin-top : 0px;      

            }

            ul#navmenu .sub2 a

            {

                  margin-left : 10px;

          }

      ul#navmenu li:hover > a

            {

                  background-color :#CFC;            

            }

      ul#navmenu li:hover a:hover :

            {

                  background-color :#FF0;            

            }

      ul#navmenu ul.sub1

            {

                  display : none;

                  position : absolute;

                  top : 26px;

                  left : 0px;                                    

            }

      ul#navmenu ul.sub2

            {

                  display : none;

                  position : absolute;

                  top : 0px;

                  left : 121px;                                        

            }

ul#navmenu li:hover .sub1

            {                

                  display :block;

            }

           

ul#navmenu .sub1 li:hover .sub2

            {                

                  display :block;

            }                

        .style1

        {

            font-size: small;

        }

    </style>

plz help me sir.