While the IE8 feature was not specifically designed to be an advertising blocker, it is expected to have that effect for certain forms of online advertising that depend on pixel tracking, because IE8's InPrivate application can block tracking pixels, cookies or pieces of code that enable third-party sites to identify and track individual browsers as they surf from site to site.
News of the IE8 ad blocking threat comes as Microsoft rival Mozilla is preparing the release of a new version of its equally popular Firefox browser. Mozilla dubbed its new feature a "private browsing" tool, and said it would offer users greater flexibility in terms of how they adjust their privacy settings, but the effect could be the same as Microsoft's IE8 privacy features.
Mozilla is planning its release for later this year or in early 2009.