I have just been viewing some of my images with zoom browser and noticed that some of them have no red square indicating the focus point, just the 19 squares in black, then there will be many where the focus square is in red indicating the focus point with the other squares in black. I have been using the single point focus mainly, and some single shot and some AIservo. I have the camera set to use the AE lock button to focus, and then AF on button to lock the exposure.
Just wondered if not having a red square indicated that I had not actually achieved focus, when I thought that I had.