代码如下：
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
<frameset cols="25%,50%,25%">
<frame src="frame_a.html"> //分别为3个html网页
<frame src="frame_b.html">
<frame src="frame_c.html">
</frameset>
</head>