Headings
The best way to provide structure to a document is with headings.
This content belongs to the heading level one, above.
Heading level 2
This content is the first section of the document, belonging to the first heading level two. You'll see lots of these.
Heading level 3
This content is the first sub-section of the heading level two. Heading
Heading level 4
This content belongs in a heading level four. These are pretty rare and are usually the deepest level of heading a document will use.
Heading level 5
Every now and again you'll see a heading level five, like this, but this is where it gets tricky to remember how many levels deep you've gone.
Heading level 6
HTML offers six levels of heading, but level six is highly unusual, and if you use it you probably need to rethink your information architecture.