Trial and error seems to have shown that the best separator between levels is the “greater than” character (>). The colon (:) and slash (/) are workable, but > seems to be the most satisfying and self-evident—probably because it visually suggests forward motion down through the levels.
Don’t make me think
Being an expert in online usability Krug gathered his experience in a wonderful book. This summary of key thoughts will help you to remember most important principles and laws.