SEO Lesson: Keyword Emphasis Counts
To rank well for a particular keyword, the target keyword must not only appear on that page, it should appear prominently:
Emphasize target keyword phrases by using them numerous times in META tags, headings, bold, italics, and/or bullets
Keyword Density
A subset of this lesson is keyword density, which refers to the proportion of a web page's text represented by the target keywords. There are many debates as to what percentage ranges are optimal for SEO. Personally, I don't approach keyword density mathematically. I use the follow guideline: use target keywords multiple times on the page, but no more than would seem reasonable to a visitor to that page.
META Tags
While it is widely believed that Google ignores META tags for ranking purposes, other search engines, such as Yahoo! do use them. As such, it is important to include both 'description' and 'keywords' meta tags on each page. Since each page is targeted to a different keyword phrase, these should be different for each page.
Headings
Use heading tags such as <h1>, <h2>, etc. to add emphasis to your target keyword phrases.
Formatting
To emphasize keywords in the main text portion of a web page, you can use them in bold, italics, or in bulleted lists.

