Headings are tagged with a heading tag of the appropriate level. There are up to 6 levels of nesting. The first or top-most heading in a document should have level 1. After each heading, a heading of any other level is possible. However, do not assign a higher level to nested headings.

Example:

1. Heading (level 1)
   1. Heading (level 2)
   2. Heading (level 2)
      1. Heading (level 3)
2. Heading (level 1)
   1. Heading (level 2)