Headers

In theory, HTML offers six levels of headers, H1 through H6. In practice, few people use more than the first two or three levels of headers because of the wide variations on how the H3 through H6 headers display on different browsers.

HTML

    <h1>
    Level One Header 
    </h1>

    <h2>
    Level Two Header 
    </h2>

    <h3>
    Level Three Header 
    </h3>

    <h4>
    Level Four Header 
    </h4>

    <h5>
    Level Five Header 
    </h5>

    <h6>
    Level Six Header 
    </h6>

How It Displays

Level One Header

Level Two Header

Level Three Header

Level Four Header

Level Five Header
Level Six Header


Specifications

From the W3Schools.Com Complete HTML/XHTML Reference: