bunny questions

Question
i noticed last week that my bunnys urine was milky in color  and today it looked brownish she drinks allot of water and we give her carrots and celery 3-5 times a week so i believe shes healthy. May you help in answering this question of mine .  
my husband and i were looking at pet smart at bunny 'litter boxes' is this for the cage or out side by the cats litter box? we have two cats who love playing with bunny.
also we are not sure if shes a she. we got her at the flea market and she was very young the seller looked and said she thought it is a girl , sounding  not sure.  and 2 weeks ago she started humping my leg , to me this seems like a male habit !!  hehe   how can i be sure bunny is actually a girl   THANK YOU for you're time an knowledge
                  Lina B

Answer
Dear Lina,

Rabbit urine can vary from white to yellow to orange to red to brown, depending on what the rabbit has been eating and his state of hydration.  Very dark urine in very small quantities suggest she is not getting enough water; if this is the case, provide a large ceramic crock full of clean water for constant access, since rabbits drink more (and more
naturally) from a bowl than from a sipper bottle.

Rabbits can be litterbox trained, as per the instructions here:

www.bio.miami.edu/hare/training.html

but first you'll have to find out if she's a he, or vice versa, since a spay/neuter is essential for good litterbox habits.  Both males and females will mount, though it's more common for males.   And spay/neuter will stop this behavior, as well.  Please read:

www.bio.miami.edu/hare/spay.html

and find a good rabbit vet to help you here:

www.rabbit.org/vets

You can try to sex your bunny with this article:

www.bio.miami.edu/hare/sexing.html

but a good rabbit vet will be able to tell if you can't.  Hope this helps.

Dana