Answer to: How can I fix Error 99 on my Canon EOS Digital Rebel?An error 99 is not anything, but is an undefined error that's not described by one of the documented error codes. That's been standard for decades. I always start with the quick-and-easy stuff. A soft pencil eraser to clean contacts on lens and body, and the battery. Visual check of memory card and compressed air to clean contacts of dirt. Similarly, my flash gave an error, and compressed air cleaned the sensor arm in the tiny hole below it, and all was well. Use low pressure and be careful. Use extra light for a good visual inspection.