Second this opinion. Doesn't matter up or down, as long as it looks neat and doesn't somehow get in the way, like LG said.
The general rule-of-thumb for appearance for interviews is: don't stand out. It kinda is that simple. Wear neat clothes, dress professionally, have your hair look neat/appropriate, wear a scant amount of perfume/cologne (or none).
Things that will hurt you - whether unfair or not:
- Dressing to stand out - either too casual or too crazy colorful or too low-cut or too high-cut. Be modest, professional, clean.
- Garish tattoos. This one comes up every year. I very much think we are at the point where nobody judges a discreet, unoffensive tattoo in 'normal' locations. But go in there with a swastika on your forehead and yeah, you're going to be judged for it. You should have guessed that when you had it done, and if you didn't, it legitimately speaks to your judgment.
- Hair looking like you just rolled out of bed.
- Too much perfume/Cologne. Err on the side of too little. It's amazing how many people put WAY TOO MUCH scent on themselves. Really amazing. It should be subtle, not in your face. If your interviewer is backing away because of the overpowering odor, it's too much. This isn't intended to be sexist, but I am amazed how many women put far too much perfume on. Maybe that is sexist. I don't know.
Look neat and professional and let your words and smile speak for you, not your clothes or your scent.