Instructions for iPad
If you've taken photos with an iPad's default camera application (app) while the iPad is not correctly oriented, the photos will be upside down.
When taking a photo, ensure that the iPad Home Button is closest to your right hand, and the rear camera is closest to your left hand / ceiling.
If your iPad is not correctly oriented, the photos will display properly on your iPad but when emailed, uploaded, or viewed in some browsers they will display upside-down. This is due to how Apple applications take and save photos.
Instructions for Android
Upside-down photos are not an issue with Android devices.