This blog is not related to the functioning of Google Custom Search at all. I landed at this Google Custom Search after visiting my friend's blog. Formats of the annotations that it supports caught my eye. It allows to upload a file that have the url's in some format and when you give any query, it searches in that url set.
Looks like this is useful in the project which I'm currently working to configure the rewriter profile. This may help me in explaining one of the junk idea I have.