HtmlButton1.aspx font size:
<html>
<head>
<title>Modifying the Appearance of an HtmlButton Control</title>
<link rel="stylesheet" href="/shared/netdemos.css">

<script language="C#" runat="server">
void saySomething ( object src, EventArgs e ) {
   switch ( ( ( HtmlButton ) src ).ID ) {
   case "Button1" :
      msg.InnerHtml = "Say something amusing here <img src='/shared/biggrin.gif'>";
      break;
   case "Button2" :
      msg.InnerHtml = "Say something boring here <img src='/shared/razz.gif'>";
      break;
   }
}
</script>
</head>

<body>
<div class="header"><h2>Modifying the Appearance of an <b>HtmlButton</b> Control</h2></div>
<hr size=1 width=92%>

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

   <p>With embedded <b>&lt;img&gt;</b> tag: </p>

   <p><button id="Button1" runat="server"
      onServerClick="saySomething">
         <img src="/shared/images/billg_1.jpg"
            onmouseover="this.src='/shared/images/billg_2.jpg'; return false"
            onmouseout="this.src='/shared/images/billg_1.jpg'; return false">
      </button>

   <p>With rollover effect: </p>

   <p><button id="Button2" runat="server"
      onServerClick="saySomething"
      style="font:13pt verdana; background-color:lightgreen;
         border-color:gray; padding:6"
      onMouseOver="this.style.backgroundColor='yellow'"
      onMouseOut="this.style.backgroundColor='lightgreen'">
         Click me too!
      </button>

   <p id="msg" runat="server" />

</form>
</div>

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

</body>
</html>