You can use this form to carry out a basic search of the site, using Google Custom Search.
I've used the ubiquitous Google search for sheer convenience, after the script which I previously used (Sphider) went tits-up. This is very much a temporary measure, until I implement this site as a dynamic database-driven site, when it will have a custom-coded search form.
The search form is on a separate page, rather than in the page header, because, on load, there's a delay whilst the script contacts Google. Putting the script in the page header would add this delay to all site pages, reducing site performance.