It is often hard to tell which is the Web's priority: helping you learn about the world or helping the world — and especially advertisers — learn about you.
But that balance is beginning to shift, to the delight of consumer advocates and the horror of industry groups. Browser makers increasingly are embracing privacy controls that could limit the ability of advertisers to track users, threatening to undermine business models that now support many popular online services.
The development is driven more by market forces than governmental action, as highlighted by the recent announcement that the maker of one of the world's most popular browsers, Firefox, is experimenting with new restrictions on the use of cookies — bits of computer code that allow companies to monitor users as they move among websites.