Add a Google search box to any site?

John Robb posts the code for adding a Google search widget to your blog (or any site, really).
However, as I read it, it seems to work with entire domains (for example, jrobb.userland.com). Sites like this whose root address is a subdirectory of a root domain (this site’s address is currently blogs.salon.com/0001111/) may not benefit from this approach. Unless I’m reading the code wrong, it appears that it can be used to search all of blogs.salon.com but not specifically my corner of it.
If I’m wrong about this or if there is a workaround, please tell me, as I would like to add search to this site.