1. For the answer to your first question if "begin" is greater than "end" then the loop is simply not executed.NO ERROR
"step" must be greater than or equal to 1 else ERROR
2. The Tag File is choosen by the name of tag you use.
for e.g
if you have a Tag File Named NavBar.tag and Header.tag in WEB-INF/tags folder then
in
jsp when you define
<%@ taglib tagdir="/WEB-INF/tags" prefix="mine" %>
<mine:Header> ----> this will invoke your Header.tag file
<mine:NavBar> ----> this will invoke your NavBar.tag file
Also remember you can name your tag file with extension as either .tag or .tagx
Hope i cleared all your doubts
Regards
Rishi Chopra