when to leave space ,when not in CSS?

Question

This is ok(without space):

li.highlight{
    background:#FF9900 none repeat scroll 0 0;
}

This will not work(with space):

l         


        

Answer 1

Because space (in a selector) means descend down the DOM to find matching tags, so:

• li.highlight
  • Means Find any list item with the class name highlight and apply this style
• li .highlight
  • Means Find any element with the class name highlight, who's ancestor is a list item, and apply this style