I have discovered that a line works all right
(ie it adds the space I want) if it ends
margin-right:20px;} also works.
padding-right:20px} does not work.
padding-right:20px;} does not work
So I am thinking my difficulty is associated with the 'padding' property. Can you have padding in a jpg image file - perhaps not?
I am reading a book (reputable publisher, Peachpit Press, marked 'Copyright 2005', so probably up-to-date) where all the style rule examples are written without a ; before the final curly/brace bracket - that's where I got the idea from in the first place.
I shall mark this thread closed, whilst I delve more into padding and margins and under what circumstances a final ; before the } is needed.
Thank you for your interest.