1. When grouping selectors, place individual selectors on a separate line.
2. Add double quotes to the attributes in the selector.
3. It is best not to exceed the 5th level selector level.
4. Each selector occupies one column. Except for the last selector, the selectors in each column end with a comma.
Example
/* bad */
.selector, .selector-secondary {
padding-left: 15px;
}
/* good */
.selector,
.selector-secondary {
padding-left: 15px;
}The above is the usage specification of CSS selector. I hope it will be helpful to everyone.