解决方法：将页面的body节点去掉，错误代码如下
复制代码 代码如下:
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>主页</title>
</head>
<body>
<frameset rows="15%,70%,15%" frameborder="yes" >
<frame scrolling="auto" src="/UploadFiles/2021-04-02/IndexTop.jsp"><frame scrolling="auto" src="IndexMain.jsp"><frame scrolling="auto" src="IndexBottom.jsp"></frameset>
</body>
</html>
由于frameset是一种框架结构，将整个页面占据掉，不要用body进行布局
复制代码 代码如下:
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>主页</title>
</head>
<body>
<frameset rows="15%,70%,15%" frameborder="yes" >
<frame scrolling="auto" src="/UploadFiles/2021-04-02/IndexTop.jsp"><frame scrolling="auto" src="IndexMain.jsp"><frame scrolling="auto" src="IndexBottom.jsp"></frameset>
</body>
</html>
由于frameset是一种框架结构，将整个页面占据掉，不要用body进行布局