<H1>...</H1>-<H6>...</H6>
Definition
This tag specifies the style and the size of the heading you prefer to make your text more orgranized and easier to read. It has six levels: <H1>...</H1> (heading level 1), <H2>...</H2> (heading level 2), <H3>...</H3> (heading level 3), <H4>...</H4> (heading level 4), <H5>...</H5> (heading level 5), <H6>...</H6> (heading level 6). By default, level 1 is larger and more pronounced than level 2 and so on.

Attributes
ALIGN=(LEFT|CENTER|RIGHT|JUSTIFY) - Sets the alignment of the header text. The default alignment is LEFT.

Use
Use this tag to add structure and divisions in your documents. It is recommended by some experts not to use sub-header levels in a main level unless you use at least two of them. This also gives an outlining principle not to indent them unless two sub-topics are under a topic.