HTML provides 6 levels of headings: H1,
H2, H3, H4, H5, and H6. These should be used to mark headings
according to their relative importance, with h1 being the most
important. Headings are block elements, and can only be created as children
of elements that have block-type content. Note that for tables of data there
are special elements to mark headings.
The first three levels of heading can be created from the toolbar using
the heading images 
, 
, 
. All levels of heading can be created from the XHTML menu,
or using keyboard shortcuts. The default keyboard shortcuts are Ctrl h
Ctrl 1 for H1, Ctrl h Ctrl 2 for
h2, and so on to Ctrl h Ctrl 6 for
h6.
There are default styles for headings in most browsers to give some idea of their relative importance, but the author can also use style sheets to provide a suggested presentation.