What Spiders Search for on Your Web Site
When search engines send out spiders to gather data on your Web site, their job is not simply to look for keywords; they also check the density, frequency, and prominence of those keywords.
Keyword density measures the number of times a keyword or keyword phrase appears on a Web page, compared to the total number of words on the page. To determine density, you take the number of words on the page (say, 1,000 for a long page) and the number of times that the word appears on that page (maybe 23 times). Divide 23 by 1,000 to get a density of about 2.3 percent. Keyword density is one of the factors a search engine spider looks at when determining whether a Web page is relevant to that search.
Keyword frequency is another factor that SEOs look at. It's simply how many times a word appears on the page; in this case, 23 times. The combination of frequency and density is the prominence — higher density and more instances lead to greater prominence of the term.
These factors collectively are why it’s important to have searchable text on your Web page, and especially on each landing page. That doesn’t mean you have to write a novel on your landing pages. Search engine spiders generally put more weight on the first 200 words on a Web site, including words in your navigation, headings, and so on. It's important to make sure that your keywords appear throughout the page but especially right up front so that search engines and your visitor know what you're all about from the get go. You can elaborate further from there on, of course.