Categories' posting have disappeared

Under posting when I select a category for it to go under and then update. When I go to the page that has that category, nothing is there. Is there something that turns posting on that page to not show up?

ie: Category name is Animals

I wrote about Dogs per se and posted under that Animals Cateogry. WHen I go to http://www.example.com/earths-animals, my posting for Dogs is no where to be found. It was there like yesterday, and I don’t remember changing anything significant…