Headings, Alt Tags, & Link Titles
Correctly using these will improve usability and boost your search engine rankings!
Headings, or H1,H2,H3, etc.
Use the headings semantically, ie what they are intended for. In his book, "designing with web standards",Jeffrey Zeldman says
Tagging a headline h1 because it is the most important headline on the page is a semantic authoring practice. Tagging a headline h1 "to make it look big" is not.
When you structure your page content, use headings (H1) and subheadings (H2,H3, etc). Your main title (within the content) should be a Heading 1 and should be located near the top of the page. Your subheading would be a Heading 2, a sub-subheading would be a Heading 3, and so forth. Use the headings to indicate importance.
When Google looks at your pages, it'll read the text within your headlines as more important. Do not misuse the headlines though. Using multiple h1 tags or putting them toward the bottom of your pages may adversely affect your search engine rankings. You don't want to anger the Google gods!
From seo101blog.com:
Search engines like to see the first three heading tags because it helps them understand what the pages of your site are about. As always, the most important tag is the Title tag in the heading section of your page, but the heading tags help reinforce the Title tag. With that said, the H1 tag should repeat the Title tag, but it does not have to be verbatim. The same keywords should appear in both tags.
How to use headers
If you're using WYSIWYG HTML editor, simply highlight your text and select "Heading 1" in the properties. If you're a HTML purist, wrap your header in H1 tags.
<h1>This is my most important header!</h1>
<h2>This is a secondary header!</h2>
<h3>This is a minor header!</h3>
Alt Tags
Alt tags are the little captions that come up when you mouse over an image (see right). You should add alt tags to all important images on each page and make them descriptive but short. Don't worry about the images that make up the layout of your pages...just the relevant ones. Alt tags will help with search engine rankings and make your site more usable. For the visually impaired, they have site readers will read the alt tag to describe the image that they can't see.
Don't overload your alt tag with keywords that don't describe the image! However, if you have a keyword that does actually describe the image, use it.
How to use alt tags
For the WYSIWYG route, select the image and enter your text into the alt tag property. For HTML, use the alt="" syntax within your img tag.
<img src="images/me_baby.jpg.jpg" alt="My little girl--she's so cute!" border="1" />
Title Link Captions
The title link captions serve the same purpose as alt tags but for links. Similarly, when you mouse over a link with a title property, you'll see a caption. Although this is a good thing to do for usability, it doesn't pack as much punch for search engine ranking as alt tags. But it definitely won't hurt your cause. =)
How to use link captions
For your HTML editor, select the link and enter your text. For the coder, add a title="" property to your a tag.
<a href="image.html" title="Return to home page">
Next step: Site Maps
Further Reading: