DataGridGridLines.aspx font size:
C# Source: DataGridGridLines.aspx   fetchData_sql.cs   
View Sample
<%@ Import namespace="System.ComponentModel" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

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

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

<script language="C#" runat="server">
void Page_Load ( Object src, EventArgs e ) {
   if ( !IsPostBack ) {
      ICollection grids = TypeDescriptor.GetConverter ( typeof ( GridLines ) ).GetStandardValues ( );
      foreach ( GridLines g in grids ) {
         GridSelect.Items.Add ( g.ToString ( ) );
      }
      GridSelect.SelectedIndex = 2;

      string query = "SELECT Lastname, Firstname, Address, City, Country FROM Employees";
      myGrid.DataSource = fetchData ( query );
      myGrid.DataBind ( );
   }
   myGrid.GridLines = ( GridLines ) GridSelect.SelectedIndex;
}
</script>
</head>

<body>
<div class="header"><h2>DataGrid GridLines Property</h2></div>
<hr size=1 width=92%>

<div align="center">

<h4><i>GridLines</i> specifies the grid line styles for controls displaying items in a table structure, such as the DataGrid.</h4>

<form runat="server">
   <p>Select gridlines <asp:dropdownlist id="GridSelect" 
      autopostback runat="server" /></p>

   <asp:datagrid id="myGrid" runat="server"
      width="92%"
      cellpadding=5
      font-size="10pt"
      headerstyle-backcolor="lightsteelblue"
      headerstyle-font-bold
      backcolor="ghostwhite" />

</form>
</div>

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

</body>
</html>