Strange this, it only turns the pictures I have took with my camera, this is a screenshot and it comes out perfick.
The reason for that is pictures on your phone often have some additional data embedded that specifies the orientation (portrait or landscape). Sometimes your camera adds this info when you take the picture, or software you use to rotate images can do it as well. This is really cool, because instead of going through the (relatively slow) process of physically rearranging the pixels to actually rotate the image, it just turns 90 degrees whenever you view it. Unfortunately, when you upload a picture, this additional data is lost. That's not just the case with image uploads on this forum btw, all uploads will discard this info. Therefore, once the image is uploaded it shows up in the "original" orientation, which in this case, is different from how it appears on your phone. Very annoying!
The best way to get around this is to get a photo app that physically rotates the image, instead of simply editing this meta-data. Then when you upload the pictures, they will appear as you see them on your phone.
Hope that makes sense!