FixedTitleRow；scrollDiv；用途解释

下面这段代码大概的用途，和意思我迟到，现在想求问大神，每句代码的意思和用途。希望有大神能给耐心解答

 <style>
        .FixedTitleRow {
            position: relative;
            top: expression( this.offsetParent.scrollTop );
            z-index: 10;
            background-color: #ffffff;
        }

        .FixedTitleColumn {
            position: relative;
            left: expression( this.parentElement.offsetParent.scrollLeft );
        }

        .FixedDataColumn {
            position: relative;
            left: expression( this.parentElement.offsetParent.parentElement.scrollLeft );
            background-color: #E6ECF0;
        }

    </style>
    <SCRIPT>
        function sHeight()
        {
            document.all("scrollDiv").style.height =document.body.clientHeight-66;

        }
    </SCRIPT>



        <div id="scrollDiv" name="scrollDiv" style="border-top:0px solid #3399FF; width:100%;
    overflow:auto;   cursor:default;   display:inline;   position:absolute;    left:10px; top:82px"
         runat="server">