What do search engines use to rank a web site?

Code (continued)
Although there are a lot of variations between different search engines and directories the one common theme is keywords. Keywords are the words you’ve chosen as the most likely words people use to search for your type of product. In our earlier example the words would be “group exercise”. If your keywords appear throughout the code, the search engines in particular are going to be much more likely to rank your site highly as an authoritative site with regards to searches using those keywords. However, when optimizing it is important to keep in mind that the search engines are on the lookout for spammers, which are programmers trying to abuse the system. Therefore, excessive use of key words can get your site banned. See “Don’t Over Stretch”.

Content
Content is the heart of a web site. The goal of all search engines and directories is to deliver web sites with the best most relevant content to its users search terms. They also want their users to be able to find the information they want fast. For this reason key words that appear sooner in the code count for more. So, as with most search engine optimization, what makes the most sense is also the best for optimization. Write quality content that pertains to your topic and make sure your key words appear frequently and higher on the page. The target for key word frequency is 3% to 7%; that is, out of every one hundred words three to seven of them are your key words. Again, beware of over stretching. If every fourth word is a key word you have two problems: your text will be unreadable and your site will be banned from the search engines for spamming.