Can not find the tag library descriptor for "http://java.sun.com/jsp/jstl/core"

You would have used this way
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core"  prefix="c" %>

You should use this, prefix should come first
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

Main thing is you will be using tomcat 7 or higher version. You need to use JSTL - 1.2.jar

you  might be simply using JSTL.jar.

just put the JSTL-1.2.jar in lib folder..