The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml...

在jsp中用JSTL标签迭代集合中元素，却出现这个异常：

org.apache.jasper.JasperException: /WEB-INF/jsp/home.jsp(3,62) PWC6188: The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application

/WEB-INF/jsp/home.jsp(3,62)文件如下：

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
${phonetic}
<br /> 
${eetymologies}
<c:forEach items="${eetymologies}" var="eetymology">
${eetymology.word}
${eetymology.eetymology}
</c:forEach>
<br /> 
${cetymology}
</body>
</html>

该jsp文件中没有错误；在项目中已经导入了JSTL需要的jar文件，也把jar文件放进了/WEB-INF/lib/中。后来发现把服务器改为Tomcat7，异常就消失了。