how to separate paragraphs? margin or padding

I think margin.

h1{margin-bottom:15px} h3{margin-bottom:12px;} p{ margin-bottom:10px }

Thats how i'd do it. Padding pushes the content within the element. Margin pushes the element away from other elements. Elements being the p/h1/h2 and content being the text inside. I think I worded that right. :P GL hope it helps

diagram

That's right, you can experiment with margin and padding using a border around your elements.

h1, h3, p { border: 1px solid black; } ***for test purposes.

Agreed. Margin is the way to go. Padding works if paragraphs have either no background or the same color background as the content area behind it. But, what if you want to make a single paragraph stand out by adding a background color to it? In that case, the background color of the paragraph will hit up against the paragraphs around it and you'll end up needed to add margin to that paragraph anyway. It's better to use margin so that you can adding a background and padding to one or more of the paragraphs if you need to, while still maintaing an equal distance between paragraph blocks. I hope that make sense!

TL;DR - Margin is the one you want.

There are few important differences between margin and padding, margins auto-collapse padding doesn't. Also padding enlarges the size of an element, e.g. it makes the clickable area of a button bigger.

Margin is on the outside of block elements while padding is on the inside.

use margin to separate the block from things outside it, padding to move the contents away from the edges of the block.

source: http://stackoverflow.com/a/2189462/1756132

For more details check out this tutorial on CSS basics from Smashing