best free search engine for website

[webnewbie]

I am trying to add search engine to my website. I'd like to have some recommendations about various free search engines that can be embedded to a website.
Is there a good one that supports css customization?

[erisco]

what about Google's site search? So long as your pages are indexed.

If your site ran off a database, like I am trying to do, searching is a breeze.