Consider editing TLD file. When editing tag/attribute/type element body, not existing class names are highlighted as errors. But package names (instead of class names) are not highlighted. I.e.
is not highlighted. It could better cause a warning.
(Running JSP using TLD with "java.lang" instead of "java.lang.String" makes NO error on Tomcat 5.5.20. So, warning looks more suitable in this case.)