CSS

css first child

:first-child {
	//styles here
}

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

css first child

/*CSS First - forth child*/
:first-child {}

:nth-child(2){}
:nth-child(3){}
:nth-child(4){}

css first child

:nth-child(1){
/* css code here */
}

css first child

selector:first-child{
  //style
  
}

css first child of type

#mainTable>tbody means first tbody of table which take id mainTable