The following new feature has been added in Safari 8.0.
Quick Website Search
A new feature, Quick Website Search, allows users to access content from a specified website directly from Safari’s Smart Search field, bypassing their normal search engine. For example, a user might type “app solitaire” to search for solitaire games on the App Store, or “wiki OS X Yosemite” to find the Wikipedia article on OS X Yosemite. The desired result would then appear at the top of the suggested completion list for that search.
In OS X, website developers can aid Safari in discovering searchable content by including an OpenSearch description document on their site, conforming to the format defined in the OpenSearch specification. After the user has visited a page on the website, the site will then show up in the Manage Websites panel of Safari’s Search Preferences, allowing the user to selectively enable or disable the Quick Website Search feature for individual websites. Although the use of OpenSearch is not strictly necessary (Safari’s heuristic is sometimes able to obtain the information it needs by other means, such as from the form metadata for search fields), it is strongly recommended that websites publish an OpenSearch description.