Thanks Keith, Frits.
I did try out the Classic and Simple tags individually. Simple tags have a problem with scripting while Classic tags dont.
Now as I have been trying to figure out, I put scripting code in a Classic tag and put that Classic Tag inside a Simple Tag. To this the container (Tomcat 6.0.20) complained, like Frits had pointed out:
Scripting elements ( <%!, <jsp:declaration, <%=, <jsp:expression, <%, <jsp:scriptlet ) are disallowed here.
So for now, I am assuming:
If there is scripting code in a Simple Tag, whether directly in it's body or not, it is not allowed.