Here's some tips about what Google uses to rank a site. Tips gathered from different sources and edited with my own experiences.
Note: Search Engine Optimization (short SEO) is about editing your site so it shows up as top result in search engines. This activity is mostly gaming, and often with underhand tactics. Note that, if you want your site to be popular, the one most important factor is to create useful content that visitor likes. However, for certain content, there are thousands of competitors. For example, if your site sell or write about cell phone, then there are thousands of sites all in the market, and most of them all have useful content.
So, SEO is not something just for the shady businesses. It is critical. Looking at it from another perspective, understanding SEO can be thought of as part of understanding marketing — a necessity of business.
The unfortunate thing about existence of SEO is that, if your site is not a commercial organization — maybe you are a professor writing about math education on your blog, or maybe you are a professional novelist writing a personal blog about creative writing, then, even if you writing is top quality content within your subject, you site may be hard to find in search engines, because of the SEO activity by thousands of commercial orgs.
The text in the HTML
<h1> tags are perhaps the most important item in how
Google determine a site's content, and suppose you have a creative-writing blog
about English lexicon, and titled your blog with a artistic name such as “the
Making of Belles-Lettres”. When people search about English vocabulary, your
writing may be what they need exactly, but because your title does not contain the
word “vocabulary” nor “English”, and fail among other 100 esoteric SEO factors, so
search engine won't show your site on top, if at all.
Many people with expertise in particular area write blogs (⁖ academicians, artists). They write as a hobby, personal notes, to share their ideas with friends or other people. They have no intention to make money out of the blog. They wouldn't know the concept of SEO. If they do, they wouldn't be spending hundreds or thousand dollars to hire SEO companies to optimize their page, nor do they have the time and expertise to know all the tech details. The general public suffer from this, because millions of sites engage in SEO activity for the sake of money, and a majority of them have little or no quality content. (they are so-called “content-farms”) So, when people search for “English vocabulary”, “math education”, “geometry”, they arrive at shady sites that sell low-quality English Tutorial or other products, and your quality blog “the Making of Belles-Lettres” went unnoticed.
Here's a list of most important factors. Main source: Source www.seomoz.org.
Google itself said there are about 200 factors. Here's a list of factors, based on Source www.seomoz.org • Source www.vaughns-1-pagers.com • Source www.webmasterworld.com.