Google is experimenting with a search feature that allows users to tailor their searches by creating a list of sites they would like to appear most in search results.
Preferred Sites will suggest frequently visited sites based on search history when it's relevant, but users can also add and delete sites, according to the new feature's help page:
The preferred sites feature lets you set your Google Web Search preferences so that your search results match your unique tastes and needs. Fill in the sites you rely on the most, and results from your preferred sites will show up more often when they're relevant to your search query.
Google said that Preferred Sites could also have an impact on everyone's searches:
If the feature goes live to everyone, people will be able to pick a list of authoritative sites and influence all search results.
Preferred Sites is an extension of Google SearchWiki, which lets people elevate, delete, add, and annotate search results. It is activated only while the user is logged in to their Google account, and users' preferred sites and search results are private.