If you find something, I would love to know what it is. I've tried everything including bleach on our bathroom floor and I can't get the grout clean.
I DO know that, once the grout is clean, that you need to use a grout sealer (a clear liquid available at hardware stores) to re-seal the grout, so it's stays cleaner longer.
Happiness is being kneaded.
Avatar is my childhood kitty, Berries.