Well all you can do it test it with the iphone upright then sideways.
I would suspect that the photo was taken in landscape to fit in the screen.
The iphone will rotate the picture to whatever orientation you hold the phone after you take the picture.
Then poof you upload it and it is sideways.
That make sense but why does it look like Portrait mode when I view the picture on the computer?
As stated in your case only the browser deals with the image file and rotates it for you.
Next time it may not.
But viewing in ubb does not,depending on how it was uploaded.
FYI the second picture attachment was perfect in portrait mode, At least for me.
