Being Aware of Initial Values in Your CSS
In CSS, every property has what’s referred to as an initial value. Sometimes this is called the default value, but the spec uses the term initial, which I think is a slightly better term.
Technically speaking, the initial value of any given property needs to be declared only if that value is overriding a previously-defined value that’s not the initial value. But initial values are often present even when they’re not necessary.
For example, suppose I have a block-level element that I want to take up the full width of its parent. I want it to sit on its own “line”, so to speak, in the layout, so I add the following CSS: