The Do Not Track feature has been designed to give Internet users a say in the matter. It is not the most effective option though as it is not mandatory for companies to comply with it if it is set by the user. While several companies honor Do Not Track, others may choose to ignore it. It is therefore reasonable to say that even with Do Not Track enabled, users are getting tracked on the Internet.
Mozilla has improved the Do Not Track feature in its Firefox web browser starting with current Nightly versions (that is version 21 of it). When you open the tracking related settings – with a click on Firefox > Options > Privacy – you will notice that you can now switch between all three states right from the menu.
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