Thanks guys...
I also got same conclusion as sujit :
<!ELEMENT taglib (tlib-version, jsp-version, short-name, uri?, display-name?,
small-icon?, large-icon?, description?, validator?, listener*, tag+) >
We are refering to
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD
JSP Tag Library
1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
This is specified in JSP2.0 Specs and according to this jsp-version is also mandatory !!!