Three basic framework of CSS

The three CSS selectors
1, css-css substantially selector (three kinds)
to be manipulated inside the tag data of which
(1) the tag selector
div {
background-Color: Red;
Color: Blue;
}

(2) class selector

• Each HTML tag has one attribute class
  
  I would like to have years can look back, and with a total of affectionate bald!
  
  .haha {
  background-color:blue;
  }

(3) id selector

• Each HTML tag has an id attribute

I would like to have years can look back, and with a total of affectionate bald!

hehe {

background-color:blue;

}

*** basic priority selector
style> id selector> class selector> tag selector