You can only use JSTL (Suns's ready made tags) if you have a copy of the correct jar in your WEB-INF/lib directory.
The name of the jar is jstl.jar and if you are running
Tomcat you can find it at webapps/jsp-examples/WEB-INF/lib/jstl.jar in your tomcat hierarchy.
Be sure to copy the jar from there into the WEB-INF/lib directory of all your web-apps that will use JSTL standard tags. This is because thay are not imported by default.
I hope this explains things. If you are not running tomcat I'm sure you can download the jar from Sun at some place.