Keyword density means the ratio of keywords that you are trying to target for SEO purposes to the other text on your pages. Getting keyword density right—enough so that your SEO goals are achieved, not so much that the search engines are “offended”—is a key goal of core SEO practice. Search engines do look for keywords, but they take away points for excessive and inappropriate keyword “stuffing.”
Even from the point of view of your site visitors, you want a nice density of keywords in your pages—but you don’t want so many keywords that the content of your pages is diminished from the viewpoint of visitors.
Here are some design and information architecture guidelines you should apply to your site to optimize it for search engines:
For most sites, the fancy graphics do not matter. If you are looking for search engine placement, it is the words that count. Always use text instead of or in addition to images to display important names, content, and links.
Do make sure you provide accurate alt attribute text for any images that are on your pages.
Pages within your site should be structured with a clear hierarchy. Several alternative site navigation mechanisms should be supplied, including at least one that is text-only. The major parts of your site should be easy to access using a site map. If your site map has more than about 100 links, you should divide the site map into separate pages.