Anything unusual like stones, a drinks can, a bottle left on a doorstep or at a gate may be a test by a burglar to see if people are away on holiday. If the stones or whatever are removed the burglar will assume there's someone at home or someone looking after the home.
It could also be a message from someone who's been spying on your home to see how vulnerable it is - e.g. one crumpled drinks can may mean one little old defenceless lady - an easy target for a burglar.
Make sure someone checks your house if you're going to be away.
nothing, there is no meaning at all.
It means that someone leaves a lime and a salt-shaker on your porch
Leaving a dead fish on someone's doorstep is a warning that they are going to be killed.
There is no specific meaning behind the three stones on the ring. The ring itself is usually an anniversary ring.
i dont know (mabe they just like your doorstep).
It probably means that she likes onyx; or considers the onyx stones pretty.
"Tres piedras" means "three stones" in English.
A pigs head on your doorstep is an ominous warning to the recipient. This means that somebody might want to hurt you.
Your house smells.
Some neighbors or friends will bring you food if you are in need of comforting... like a death of a family member or loss of some kind. Its typically a gesture of kindness.
Traditionally, finding a penny is a sign of good luck. However, in Canada, where pennies are about to be phased out, finding pennies on your doorstep will soon mean that someone thinks you are in the scrap copper business.
Could mean anything, but my guess is your cat brought you a present.