The Guidelines are broken into several sections, describing aspects such as exact dimensions for buttons and windows, how and where an iPhone is likely to be used, and Apple's guiding principles, including "simplicity," "adaptability" and "consistency." Apple places particular emphasis on this last point, suggesting that developers mimic the iPhone's native controls as closely as possible, using CSS styles as a way of conforming even standard websites to iPhone users. The introduction of the guide contains wording, however, that suggests Apple still intends to allow installed software on iPhones eventually, despite the company having broken hacks with its 1.1.1 firmware update. Unofficial software has included everything from chat clients to game emulators. "Currently," the introduction reads, "developers create web applications for iPhone, not native applications. Therefore, this document focuses solely on the presentation of web applications and other web content on iPhone."