I was making a poster when a friend of mine said I should make the right margin wider than the left and she was very surprised when I didn't know of this rule. She said it was as well-known as the golden ratio. Is this true? In that case what is that rule called? I've only used different margins for books and that sort of stuff, not as a general rule.
Well, it sounds more like a 'fixed idea' rather than some "golden rule."
Most of the time, the outside margins of a book have more space...ie the copy comes in to allow for numerous reasons but the historical reason was wear and tear.
The edges of pages would inevitably get thumbed, folded and such the most..hard covers could only provide so much protection. So, by increasing the margins, the content had a little more room to 'weather the book' and such.
As for posters, I can offer that the worlds foremost designers throughout time have not adhered to any such rule.
What she may have meant, was the western tradition of shorter line lengths when adding larger amounts of copy. Since we read from right to left, a wider right margin provides a quicker return.
But again, that's only when we're talking about too much copy for a poster anyway.
The "rule of thirds" is different and really just an organzing method no better or worse than any grid layout.
When I was in school, to suggest that such a rule determines the creative and design/layout of a poster would have led to public hanging and retiring of all my tools of the time... xacto knife, harbor rule, french curves, pantone books etc.
Don't sweat it. The aesthetics of design are more important; the formal aspects of design (balance, composition, harmony etc) have been proven since only about 2000 bc! Even the earliest know civilization of catal hyuk (don't remember the correct spelling) practiced balancing and composition even if not as successfully as the early and high rennaissance.
Wider to the right? If the design so deems it. Or, only if the printer is terrible at trimming and you know which way the press sheet is running!