Nesting rules:
- do not use IDs in nesting; use classes instead; more than one same ID makes page not valid and it is hard to select few similar elements with css or javascript; (bad: #title; good: .title)
- do not use !important;
- do not use tags in nesting; use only classes; it is easier to change tags in template later; (bad: div.title; good: .title - because div.title could be changed to section.title in future)
- do not use "_" (underscore) in classes; use "-" (hyphen) instead; (bad: .main_title; good: .main-title)
- a heading should not become a heading in another part of the page;
- class names should be abstract; what is red today could be blue in future; (bad: .red-block; good: .news-block;)