If you are using (uses JSTL 1.2)
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
means to use EL Expressions you do not need <c:out>. You can directly insert EL expressions onto jsp page like ${propertyName}
While using (uses JSTL 1.0 deprecated)
<%@taglib prefix="c" uri="http://java.sun.com/jsp/core" %>
You can not use EL Expressions directly on jsp page you need <c:out>. EL expressions on the page will not work. e.g. <c:out value=”${propertyName}”>.
Also your web-app version (found in web.xml) should be down to 2.3 to use http://java.sun.com/jsp/core which is again too old.
Conclusion:
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> - Can use EL directly
<%@taglib prefix="c" uri="http://java.sun.com/jsp/core" %> - Can not use EL directly
