HTML supports six levels of heading, from <h1< (the largest) to <h6< (the smallest). It's rare for anyone to use any heading smaller than <h4>
Let's start by styling <h1>which is usually used for the main title of a Web page:
h1 {margin-left: -25px; font-family: sans-serif}
Again, the font used is sans-serif -- I think that heading in a serif font looks a bit too staid whether in print or on the Web.
Notice, though, that I set the margin-left property to -25 pixels. This creates with effect that I alluded to earlier. All headings that are tagged as <h1>will be 25 pixels to the left of the body text. This effect is called an outdent.
In many structured documents, not all headings are outdented to the same degree. A first level heading has the largest outdent, and all other headings move to the right. Using that as a guideline, let's style <h2>like this:
h2 {margin-left: -15px; font-family: sans-serif}
The outdent for <h2>is five pixels smaller than for <h1>.The font is, you guessed it, sans-serif.
Now, for <h3<. Some people like to have <h3>outdented. Not me. I like it in line with body text. So, here's how to create that effect:
h3 {font-family: sans-serif}
Notice that I didn't include a margin-left property with this style definition. It's not needed.