Ive had the same issue. Sometimes when I upload an image it will come up on the post sideways, even though in the file and on the phone i use as a camera the image is upright. Totally unexceptable!!! :stupidcomp:
You could also try turning the camera sideways when you take a picture so it will be straight when uploaded.
Whatever the photo viewer is called that comes with windows lets you rotate the picture and if you close the program with the picture rotated it will save it that way. Sometimes I'll have a glitchy pic that will look straight but post sideways. The only way to fix it is to open the picture with a photo editor rotate it and save it as a new picture.
Its your phone - it adds a tag to the image so it knows which way is up. Computers don't understand so place it at the expected orientation - usually sideways. You need to open in an editor and simply turn to correct orientation and save - this removes the tag as well.