You can no longer opt out of being tracked when you use Yahoo services.

Yahoo announced on its global public policy blog that as of this week, "web browser Do Not Track settings will no longer be enabled on Yahoo."

That means the requests of users who indicate in their browser privacy settings that they don't want their online behaviour monitored on Yahoo sites will be ignored.

Many web companies, including giants such as Google and Yahoo, track user behaviour by default in order to mine data and to serve up targeted advertising and personalized search results.

Several years ago, a collaboration of internet researchers, advocacy groups and technology companies proposed giving users a universal option to opt out of this kind of tracking.

In the past three years, most web browsers have started letting users select "Do Not Track" within their privacy settings. However, there is no requirement for websites to acknowledge the setting in any way or to honour the request.

"While some third parties have committed to honour Do Not Track, many more have not," acknowledges the Do Not Track website maintained by Jonathan Mayer and Arvin Narayanan, researchers affiliated with the Center for Internet and Society at Stanford University's law school.

Google's Chrome help site says that as of October 2012 "most web services, including Google's, do not alter their behaviour or change their services upon receiving Do Not Track requests."

Yahoo wrote in its blog that it had been the "first major tech company" to begin honouring the Do Not Track feature, but subsequently, the "broader tech industry" has failed to adopt a single effective, easy-to-use standard for implementation.

"Users can still manage their privacy on Yahoo while benefiting from a personalized web experience," added the blog post by the Yahoo Privacy Team.

The Do Not Track website has a short list of technology companies that do honour Do Not Track requests, including Pinterest and Twitter.