title: java.lang.NoClassDefFoundError: javax/servlet/jsp/tagext/TagLibraryValidator
body: <p>I followed the guide in <a href="https://stackoverflow.com/tags/jstl/info">this link</a> to install JSTL but I got the following error when I tried to launch my JSP page:</p>
  
  <blockquote>
    <p>java.lang.NoClassDefFoundError: javax/servlet/jsp/tagext/TagLibraryValidator</p>
  </blockquote>
  
  <p>The taglib declaration is:</p>
  
  <pre><code>&lt;%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %&gt;
  </code></pre>
  
  <p>I installed JSTL 1.1 under <code>/WEB-INF/lib</code> in Tomcat webapps and tried to do the same in my project, but it didn't work. I also tried version 1.2 of JSTL and still the same message. How is this caused and how can I solve it?</p>