document: Cat and mouse : content delivery tradeoffs in web access Web pages include extraneous material that may be viewed as undesirable by a user . Increasingly many Web sites also require users to register to access either all or portions of the site . Such tension between content owners and users has resulted in a `` cat and mouse '' game between content provided and how users access it . We carried out a measurement-based study to understand the nature of extraneous content and its impact on performance as perceived by users . We characterize how this content is distributed and the effectiveness of blocking mechanisms to stop it as well as countermeasures taken by content owners to negate such mechanisms . We also examine sites that require some form of registration to control access and the attempts made to circumvent it . Results from our study show that extraneous content exists on a majority of popular pages and that a 25-30 % reduction in downloaded objects and bytes with corresponding latency reduction can be attained by blocking such content . The top ten advertisement delivering companies delivered 40 % of all URLs matched as ads in our study . Both the server name and the remainder of the URL are important in matching a URL as an ad . A majority of popular sites require some form of registration and for such sites users can obtain an account from a shared public database . We discuss future measures and countermeasures on the part of each side .
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