Tomcat "HTTP Status 404 - /" Error

Hi All,
I had tomcat5.5.9 setup and working fine except that I was not able to connect to the database.
So I tried to be smart (bad idea) and made changes to web.xml, server.xml, and resin.conf (Trying to fix the database connection).
Now tomcat is not working

and giving me this error:

************************************
HTTP Status 404 - /
--------------------------------------------------------------------------------
type Status report
message /
description The requested resource (/) is not available.
--------------------------------------------------------------------------------
Apache Tomcat/5.5.9
************************************

I did not setup the server or any thing I'm just a developer; servers are somewhere I don't know and don't have control on.
I was given access to the server to try to fix the problem [It's their fault right

]

This is my first post, of course new to JSP and tomcat and all that...
I've been stuck for a month now

Any help would be greatly appreciated
Thank you in advance

Cheers