CSS: testing whitespace in parsing

Whitespace in CSS can either be taken into account or ignored by a parser. It depends on the context where whitespace occurs. For example:

div {
    
    color: green;
    
}

p{color:gray;}

In this context, whitespace is ignored. But in another context like this:

p span {color: teal;}

whitespace is significant because it actually identifies a descendant selector.

Example

Significant and non-significant whitespace