Felines are natural grazers, even though they are basically carnivores; when you see your cat nibbling on grass, she may not have an upset stomach - she is just doing what comes naturally.

Chocolate, caffeine, onion, garlic, and any onion-family veggetables are toxic to cats.  Just one bite of onion is enough to kill your kitty.  Onions cause a reaction called "Heinz anemia" whereby the red blood cells spilt and lose the ability to carry life-sustaining oxygen.  Death can occur very quickly.
Caffeine send a cat's heart into overdrive and the cat can die very quickly of arrythmyia.
If you think your cat has ingested any of these substances, call your vet immediately.

Cats cannot see in complete darkness.  A cat's eye magnifies the available light so they can see much better than humans in dimly lit situations.

Cats can live a healthy, happy life indoors.  Unlike a dog, you cannot confine your cat to a fenced yard, and a cat roaming the neighborhood is in danger of being killed by traffic (cats do not know how to cross a road) or contracting an infection or disease from other animals.  A cat's life expectancy is greatly increased when she lives indoors (some estimates are 7-8 years longer life expectancy).

Cats do not have an inbred fear of dogs; cats simply react to past experience or aggressive behavior on the part of the dog
(my golden retriever mix "helps" me raise the orphan kittens!  She nuzzles them when they cry, licks them if they are wet, and snuggles with them)
However, I would never leave a large dog and cat together alone; especially if the pair likes to "play" - dogs can hurt a cat, simply because they are a lot bigger than cats and sometimes do not know their own strength.