Welcome to iPhone 101, the series that explains the basics of iPhone operation.
A friend told me his iPhone was broken because the screen no longer rotated in Safari, Mail or any other app. He suspected the accelerometer was broken, but was confused because it still worked in games and apps like Google Maps.
He remarked how frustrating it was, and that he'd booked an appointment with a Apple Genius.
I must admit, I was flummoxed, too. I know you can lock and unlock the screen rotation in the settings section on iOS for iPad, but I couldn't find any such option in Settings on iOS for iPhone.
And then it suddenly hit me, there is a screen rotation lock / unlock button when you double tap the Home button and flick to the right -- where the Music player controls are. Sure enough, my friend's iPhone screen rotation was locked. With a simple tap, his screen rotated once more.
After a quick search on Apple's support forums -- and there seem to be a lot of people who struggle with this -- I found a support page which details the steps to lock and unlock screen rotation on iPhone and iPod touch.
- Double-click the Home button to display recently used apps.
- Flick from left to right along the bottom of the screen.
- Tap the Screen Rotation Lock button on the bottom left of the screen.
- If the button used to show a padlock, the padlock will disappear from the button after tapping it.
To lock the screen rotation, simply tap the button again, the padlock will appear to indicate it's locked again.