DataGridShowHeader.aspx font size:
C# Source: DataGridShowHeader.aspx   fetchData_oledb.cs   
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDb" %>

<html>
<head>
<title>DataGrid ShowHeader Property</title>
<link rel="stylesheet" href="/shared/netdemos.css">

<script language="C#" runat="server" src="fetchData_oledb.cs" />

<script language="C#" runat="server">
   void Page_Load ( Object src, EventArgs e ) {
      if ( !IsPostBack ) {
         string query = "SELECT * FROM SalesByEmployee";
         myGrid.DataSource = fetchData ( query, "dbtutor" );
         myGrid.DataBind ( );
      }
   }

   void ShowHide ( Object src, EventArgs E ) {
      myGrid.ShowHeader = myGrid.ShowHeader ? false : true;
      myButton.Text = myGrid.ShowHeader ? "Hide header" : "Show header";
   }
</script>
</head>

<body>
<!-- #include virtual="~/shared/top.inc" -->
<div class="header"><h2>DataGrid ShowHeader Property</h2></div>

<hr size=1 width=92%>

<div align="center">
<form runat="server">
   <asp:button id="myButton" runat="server" 
      text="Hide header"
      font-bold=true
      backcolor="navy"
      forecolor="gold"
      onClick="ShowHide" />

   <p>
   <asp:datagrid id="myGrid" runat="server"
      cellpadding=5>

      <headerstyle
         backcolor="maroon"
         forecolor="khaki"
         font-bold
         font-italic />

   </asp:datagrid>

</form>
</div>

<hr size=1 width=92%>
<!-- #include virtual="~/shared/viewsrc.inc" -->

</body>
</html>