Incorporating jstl tags in a jsp page allows you to do some nifty things but if you’re working in IntelliJ, the debugging can be a bit frustrating. Seeing the code snippet turn red tells you there is a syntax error or you forgot to include a library but if your code looks clean then you may be at a loss when you build and run your project and then see this image The generic 500 error doesn’t tell much but going back to the jsp page you are trying to troubleshoot and hitting the 
(hovering your mouse in the upper right hand side of the page in the project explorer will show these icons) will force IntelliJ to render the page thus allowing you to see the specific error (like this image) that is causing the problem. Adding “http://java.sun.com/jstl/core” as the “uri” in the “taglib” definition/directive at the top of the jsp page helped as well as adding the “standard-1.1.2.jar” and the “jstl-1.2.jar” to Tomcat’s lib folder (I’m running version 6.0.35) and as dependencies in the project’s Modules and added them to the project’s Libraries worked for me.