JSTL taglibs

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Your setup/config for JSTL seems ok for the most part.
You shouldn't need c.tld anywhere in the WEB-INF directory.
It is already encapsulated in standard.jar.
All you need to run JSTL are the jar files in the WEB-INF/lib directory. Anything else is unnecessary extra, and can actually hurt rather than help.

>java.lang.NoClassDefFoundError: javax/servlet/jsp/tagext/Tag
The class not found is a standard part of the JSP/Servlet API - not actually part of JSTL. The class should already be present via the jsp-api.jar file in [TOMCAT]/common/lib directory.
Sometimes the "classNotFound" error occurs if the class appears twice in the classpath.

Have you got any other jar files in your web-inf/lib directory that might conflict with this? maybe j2ee.jar?
You should NOT have servlet.jar, servlet-api.jar, jsp-api.jar or ANY jar file that has the jsp/servlet classes in your WEB-INF/lib directory, as they confuse the container.
Also check the /shared/lib directory

Maybe try it from scratch with a completely new web app.
Put ONLY jstl.jar and standard.jar in the WEB-INF/lib directory