I am new to SharePoint. I am trying to add a banner image and also
date and time display on the home page of a subsite (WSS 2.0) that was
created for my team. So presumably I need to update the css and
default.aspx file. My question is how to locate these files on the
server directory that are specific to my subsite? I don't want to do
anything that may affect the top level site. I do have admin access
to the server.

Any suggestion would be greatly appreciated.