Seo basic concept: What is the keyword density better?

Many Seo predecessors have answered this question. The answer is: 2-8%, 3-7%, less than 10%, or 5%. Choose one. Keyword density is a fuzzy concept rather than an absolute one.

The higher the keyword density, the better. In the following explanation, you may understand what the keyword density means?

The workflow of the search engine is like this:

1. Index webpages. This is the work of robot. Search robots are very diligent, so it is the easiest thing to be indexed. (But many people complain: Why is my website not included ?)
2. Classify and archive webpages by keywords.
3. Sorts all webpages in a keyword archive. This involves domain name PR value, link anchor text, and so on.
4. For popular keywords, the static page is generated on the first page of the result. (Skip this step if you do not understand it)

Second, the search engine determines the words in the webpage content that meet the keyword density standard as the keywords of the webpage. So what does keyword density mean? If the keyword density is not determined, it is impossible to rank the third point.

From: http://www.seowhy.com/2_44_zh.html