I have noticed on the forum that posted photo's appear "sideways on" in certain circumstances, why is this? And what can be done to stop this happening?

I think the software on the forum reads the exif details that the camera adds to each photo part of which is info on the orientation of the camera when the photo was taken.

Ways to cure it include always taking the picture in the orientation which you want to post it or use a slightly more sophisticated software to edit photo's which corrects the exif data at the time of editing.

I use version 18 of this program that I bought on-line

https://www.acdsee.com/en/products/acdsee

Its a lot less expensive and a lot less complicated than programs like paint shop pro.

Sometimes I download these images and rotate them so I can see them better.

Right click on an image and select "save as" or whatever the form is in your web browser.

Good thinking Nev, after reading your first bit using a photo editor I might have a go editing with Picassa if I ever have to post photo's, That should get ride of any orientation problems.

This is a common happening when people take photos on a mobile phone or tablet (most probably Apple) and import them into a Windows machine for upload to the forum / sending via e-mail, or send a photo directly to a Windows user via the phone/tablet. Windows ignores the EXIF tags which record the orientation information in the photograph. On an iPhone you can use the volume up button (+) to take a photo when in camera mode instead of pressing the screen. If you make sure this button is at the bottom (when holding the phone in landscape mode) the photo will be orientated correctly for Windows. Mac users need not worry as Apple computers use the tags correctly.