Using cell phones to explore websites that are not optimized for mobile devices can be a frustrating experience. Libraries should consider this more than an aesthetic issue, since mobile devices are the primary Internet access point for a growing number of their users. Almost 90 percent of U.S. adults now own a cell phone of some kind, and 55 percent of them use their phones to go online, according to a June report by the Pew Internet and American Life Project. Seventeen percent of respondents said they do “most” of their online browsing on their phone.