some browsers and firewalls will prohibit loading or accessing files from the users computer, but otherwise try this:
file:///C:/w.gif

my question applies to servlets, but i am hoping it is the same for jsp, how do I stop a page from continuing, sort of like
System.exit(0);

if I do this in tomcat, it will cause tomcat to...

i mean like a get (from url) or posted (client connection) variable

that wont work because i need it to be serverside, otherwise i might as well do it in html/javascript instead of jsp

I am in the process of learning JSP and my question is how do I check to see if a variable exists? The equivalent of this in php would be
if (isset($_POST['someVar'])) or
if...

http://cs.saddleback.edu/rwatkins/CS4B/Section13/Section13.html
there are instructions on how to set up tomcat 3 once you have this running and are familiar with this I would recommend upgrading...

do you want all html pages to be treated as jsp? modify your .htaccess file and AddType so that your html will be handled as jsp files, this is generally a bad idea, but you can do it if you want too

http://hostitnow.com/budget.php
for $5.00/month you can get PHP/JSP (tomcat)/MySQL/PostgreSQL/Apache/ASP (chilisoft i believe) hosting, there not the greatest of web hosts, but for that price it's...

http://cs.saddleback.edu/rwatkins/CS4B/ExamplesIndex.html
go there, there is even a GREAT explanation of how to setup and run tomcat server on your computer under "Servlets, Beans, JSPs, and CGI"...