Selectors

Type selector	Selects all elements with specified type	A
ID selector	Selects an element with specific id	#id
Descendant selector	Selects an element inside another	div a
Class selector	Selects an element with a specific class name	.class
Universal selector	Selects all elements	*
Adjacent sibling selector	Selects elements that directly follows another element	a + div
General sibling selector	Select all siblings in another element	A ~ B
Child selector	Select direct child of an element	A > B
First child	Selects first child of an element	A:first:child
Only child pseudo selector	Selects an element that is the only element inside another	:only-child
Attribute selector	Selects an element with an specific attribute	[for]

Positioning

Relative	Elements position is realtive to its default position	position:relative
Absolute	Element positioned relative to its closes positioned parent element	position:absolute