Is your image appearing on it's side or upside down? 
Worry not - this is an easy fix!

Images us orientation tags to tell programs essentially "this side up!" - but sometimes certain devices use orientation tags that not all software can understand. When this happens, all you need to do is open the image in an image editing program, and re-save it.

Sometimes you may want to rotate the image a full 360 degrees and save it, just to make sure the new orientation tag is saved correctly.

Not all image editors are created equal -  programs like Photoshop or GIMP often reveal orientation discrepancies, whereas paint or other simplistic editors might make a best guess as to the image orientation, so it might appear okay, when really it's saved as a horizontal image when it should be vertical.  This is why sometimes your image looks okay and normal before you upload it to the site.