What all should I know about web.xml apart from element name and their usage ?
The SINGLE most important JSP configuration parameter of ALL TIME is in your web.xml. Ladies and gentlemen, I give you... the TRIM-DIRECTIVE-WHITESPACES option!
<jsp-config>
<jsp-property-group>
<url-pattern>*.jsp</url-pattern>
<trim-directive-whitespaces>true</trim-directive-whitespaces>
</jsp-property-group>
</jsp-config>
This removes all the hundreds or thousands of lines of white space that you'll get in your generated HTML if you use any tag libraries (loops are particularly ugly & wasteful).
The other big one is the default web page (the page you get automatically sent to when you don't enter a web page in the URL):
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>