How to write a proper CSS

Our standard way of writing CSS should be as below:

body  {
  width: 100%;
}

Note that there are 2 spaces after body, and 2 spaces in front of attribute, width. Writing CSS shouldn't be in one line, even its short.

CSS should also be written in alphabetically, or group nicely, example below:

a  {
  color: #000;    //alphabet c first   
  text-decoration: underline;  //then alphabet t
}
body  {
  width: 100%;
}