For many people, BACKGROUND: none transparent scroll repeat 0% 0%; is wrong
but the system will help you explain it as follows.
BACKGROUND: transparent none repeat scroll 0% 0%;
respectively represent
Background attributes: background color, background image, whether the background repeats the background when the browser scrolls, background flat position, background vertical position
background : background-color || background-image || background-repeat || background-attachment || background-position
transparent means transparent and no color
none means no background image is set
repeat means Image repetition
scroll means that the background image scrolls as the browser pulls down
0% horizontal position at x0
0% vertical position at y0
This setting is the default setting for background,
That is to say, it will use this setting when the background attribute is not set.