CSS

css first

:first-of-type {
	//styles here
}

:first-child {
	//styles here
}

:nth-child(1) { //the benefit of this is you can do it for 2nd, 3rd etc...
	//styles here 
}

css first element

p:first-child {
  font-size: 1.5em;
}

select first div css

#content div:first-child {
/*css*/
}

select first div css

#content_id div.class_name:first-child {
	/*your style*/
}