With mobility having transformed from novelty to necessity, millions of Web sites are being optimized to better serve users who access them via mobile devices. The mobile devices people use to access these sites are also changing. Laptops and tablet PCs remain common, but more than ever, people are surfing the Web on their smartphones, using preinstalled mobile-browser software. In many cases, this software is proprietary, and depending on a user's network or location, Web browsing speeds can vary wildly.

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To keep the click count high, more Web sites are offering users a mobile version of existing sites. Due to phones' small screens, cumbersome interface and differing speeds, these mobile sites, often at a URL such as http://m.sitename.com or http://www.sitename.mobi, typically display fewer and lower-resolution graphics and feature hyperlinks to only the most pertinent information. YouTube, for example, has a mobile site at http://m.youtube.com that serves up videos to users on BlackBerrys and iPhones. BlackBerrys and iPhones don't support Flash, the standard video format YouTube uses. So the mobile site streams videos in Real Time Streaming Protocol (