Spraying, marking or inappropiate litter boxes habits seems to be the number reason for surrendering a cat to rescue or shelters. The owners are understandable frustrated at smell, damage and mess. Understanding why a cat has suddenly taken to spraying or marking (when spayed or neutered) can be simple to complex. Sometimes it can be a simple, treatable medical problem such as Urinary tract infection (UTI) or a bit more complecated such as FUS. Even more complicated are the behavioral reasons. Your cat might not feel comfortable with the number of cats you have, or may be picked upon by a cat in the household when he or she is most vulnerable, while trying to use the litter box! The location of the litter box may not be proper, to close to food and water, too much in the open, next to a sleeping area or high traffic area. There may not be enough litter boxes for the number of cats you have, some cats prefer to deficate in one box and urinate in another, some cats are very fastidious and if the litter box is smelly (too much elmination, or deoderizers) they may choose to go elsewhere. Some cats do not like the tactile feel of some types of litterbox materials. Anxiety, such as fear of other animals, your abscence or a change in the household or environment. The list goes on and on. SO please take a moment to browse these informative sites. Also listed below are some odor/stain remover products as well as deterrants that work quite well! Good Luck!
http://www.Spraying-and-Marking.com/
http://web.vet.cornell.edu/public/FHC/behav.html
http://kingstownecatclinic.com/Elimination%20Disorders.htm
http://www.ddfl.org/behavior/lbox_prob_prev.htm
http://www.vetmed.wsu.edu/behavior/elimination.htm
http://www.vetmed.wsu.edu/behavior/spraying.htm
http://www.spraying-and-marking.com/
http://www.feline-behavior.com/
http://www.petplanet.co.uk/petplanet/health/behaviour_caturination.htm
Odor and Urine products.
Natures Miracle, Pets 'N People, INC.
available at most pet/feed stores and online pet stores.