Nesting
When CSS is well coded, structured you will need to use many ID selectors. That’s because other selector properties can be specify trough others.
When you remove other selectors “help” and you are using just HTML, you will have a result like this :
When we are separating selectors with space, authomaticaly we say that- ” h1 inside of ID top is color #ff0 and p inside ID is red and bold.”
Easily can be tricky, because can be more than two – three levels, and you need time to practice bit.
Grouping
Grouping offers you the chance to give same properties to more selectors, and no have to repeat them separating the selectors with commas.
Or you could make it :
