When Google introduce Adsense for Search, some of the bloggers may delete the code for their search function and the replace them with Google Search. This is because when user click on the ads shown on the search result page, blog owner will get paid.
Google search is not as good as the initial search embeded in Google because new post will not be included in Google Search. Google Search on a blog is only update when it is spidered, unless your blog is frequently update, spider is now schedule to crawl your homepage daily.
All you have to do is to add a code on the url to search the wordpress blog. Blog must be powered by WordPress. You just add a small code /?s= behind the domain.
For example:
Search term is “WordPress Plugins”
Type in your browser: http://www.blog-url.com/?s=Wordpress+Plugins
Yep, thats the way to do it. simple and effective
fast and accurate result