Eclipse error "Cannot find the tag library descriptor for "http://java.sun.com/jsp/jstl/core" ideally have couple of reasons, most of them have been pointed out in the previous posts, the one and particularly important is as below. (which was actually the case with me)
Having this added in your jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
even after you have jstl.jar and standard.jar in the WEB-INF/lib directory, the only reason for this is the version of these two jar's.
defining taglib in the way "<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> " is required to have these jar's of version 1.2 (which are extracted from jakarta-taglibs-standard-1.1.2.zip) unfortunately you can never know the version of these jar's from their property
defining taglib in the way "<%@ taglib uri="http://java.sun.com/jstl/core" will require 1.0 version of these jar's.
Hope it helps.