Book excerpt: Macs run smoothly most of the time. This book will prepare you for the rare occasions when yours doesn't. Whether you're using an iMac, MacBook, or Macbook Air, our Superguide is filled with solutions for many of the common problems that you might run into. In the United States, when you're in real trouble you have but one number to call: 911. Back in 2000, while we were racking our brains for a title for Macworld's tips and troubleshooting column, we invoked this emergency calling code, preceding it with "Mac" so that its humble author (me) wouldn't be additionally inundated with requests for help with small appliances and domestic disputes. Thus Mac 911became the primary place to go within Macworld's pages for help with all things Apple. We've distilled the Mac troubleshooting knowledge we've acquired over the past 10 years of putting together columns, and created the Mac Troubleshooting Superguide, the latest in Macworld's popular Superguide series. Since the Mac 911 column's birth, we've seen the death (OS 9) and rebirth (OS X) of the Mac OS, the coming and going of countless Mac models, and the explosion of the Internet. We've also witnessed the metamorphosis of Apple the computer company into Apple the media and telecommunications giant, responsible for two of the most game-changing products of the young century, the iPod and iPhone. Yet through all these changes, one constant remains: the desktops and laptops that we increasingly rely on for our work and pleasure sometimes act up in frustrating ways. Fortunately, as exasperating as these hiccups may be, they are often predictable. In this guide, we attempt to present the difficulties you might encounter in the order in which you're likely to encounter them. If, for example, something goes amiss as you're installing the latest greatest version of OS X, you can be assured that you'll find it in the first chapter, Installation. If, later in the day, you press your Mac's power button and nothing good results, you'll find help in the next chapter, which addresses start-up issues, crashes, and freezes. Have a problem with hardware next? Simply page on to Hardware Help. And so on through the System Issues & Fixes, OS X's Applications, the Internet & Networking, and Mac Maintenance chapters. And if, despite all of your diligent efforts, no solution is found, there are directions for what to do next in the Support Tricks chapter. But allow me to also extend a personal invitation to Macworld's Mac 911 forum, where I and other knowledgeable Mac users are eager to lend a helping hand.