Best riddles with simple answers

What has four legs, but can't walk?

What goes through a door but never goes in and never comes out?

What happens when you throw a blue rock into the yellow sea?

I am small. I can be scary. I have eight legs. I spin a web. What am I?

Thirty white horses on a red hill. First they champ, Then they stamp, Then they stand still. Who are they?

What has a neck but no head?

Slayer of regrets, old and new, sought by many, found by few. What am I?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth I am dissolved into air. What am I?

I am always hungry and will die if not fed, whatever I touch will soon turn red.

What do computer programmers sing in the shower?