Google, and the other search engines, should develop a standard that allows a page to tell the search engine if it does this kind of thing. More generally, it should be able to tell the search engine which of these categories the page falls under:<p>• Freely readable with no need to register. E.g., Stack Exchange.<p>• Site requires login, but accounts are generally free. E.g., Quora.<p>• Site requires login, accounts are not necessarily free. E.g., Wall Street Journal.<p>• Per article fee. E.g., many scientific journals.<p>• Content not actually available online. E.g., many hits on Google Books, where they have excerpts of the book online so you can find it via search, but to actually get the full content you have to by the physical book.<p>Users could then choose to exclude some categories from their search results, or to have some shown ahead of others.