When o (in Spanish) is wrriten with tilde and when not?

Question

Here is an example from the dictionary: (25 ó 26 invitados)

Answer 1

La conjunción disyuntiva "o", no lleva normalmente tilde, salvo cuando aparece escrita entre dos cifras para evitar que se confunda con el cero.

I believe this rule was just eliminated back in December 2010, where it is no longer necessary to put an accent over the o.

Answer 2

When it is between two numbers.