RegexValidator1.aspx font size:
View Sample
<%@ Page clienttarget=downlevel %>

<html>
<head>
<title>Simple RegularExpressionValidator Sample</title>
<link rel="stylesheet" href="/shared/netdemos.css">

<script language="C#" runat="server">
void ValidateBtnClick ( object src, EventArgs e ) {
   if ( Page.IsValid ) {
      lblmsg.Text = "Page is valid!";
   }
   else {
      lblmsg.Text = "Zip code must be 5 numeric digits";
   }
}
</script>
</head>

<body>
<!-- #include virtual="~/shared/top.inc -->
<div class="header"><h2>Simple RegularExpressionValidator Sample</h2></div>

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

<div align="center">
<form runat="server">

<table bgcolor="#eeeeee" cellpadding=10>
<tr>
   <th colspan=2><b>Enter a 5 digit zip code</b></th></tr>
<tr valign="top">
   <td align=right>Zip Code:</td>
   <td><asp:textbox id="TextBox1" runat="server" /></td></tr>
<tr align="center">
   <td colspan=2>
      <asp:requiredfieldvalidator runat="server"
         controltovalidate="TextBox1"
         display="dynamic"
         errormessage="Field cannot be blank" />
   </td></tr>

<tr>
   <td colspan=2 align="center"><asp:button text="Validate" onClick="ValidateBtnClick" runat="server" /></td></tr>
</table>

<p><asp:label id="lblmsg" runat="server" />

<asp:regularexpressionvalidator runat="server"
   controltovalidate="TextBox1"
   validationexpression="^\d{5}$" />

</form>
</div>

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

</body>
</html>