1.Multiples,Size,and Origin
eg:background-image:url(bg.png),url(bullet.png) 0 50% no-repeat,url(arrow.png) right no-repeat
background-image
background-color
background-position
background-size:auto length percentage contain cover
background-repeat
backgound-origin:border-box padding-box conten-box
backgound-clip
background-attachment