Most Important SEO Factors for website Ranking

1. Title Tag
This is what appears in the blue bar at the top of your browser, it comes from a metatag called "title". As well as being used as a pure factor in SERP, it also boosts rank in other ways. Some
engines use “click-through” rates as a factor. Sites where the title closely matches the content tend to get better click-throughs (searchers see its not a spam site). When words in the title are also used as anchor text in a link to the page, you get more benefit.

2. Anchor Text of Links
The phrasing, terms, order and length of a link's anchor text is one of the largest factors taken into account by the major search engines for ranking. Specific anchor text links help a site to rank better for that particular term/phrase at the search engines. In other words, it’s the actual text that represents the link on a web page.

3. Keyword Use in Document Text
Your keywords must appear in the actual copy of the page. Supposedly search engines pay more attention to the first and last paragraphs. The way to go about this is have your keywords firmly
in your mind as you write your copy. I don’t know about you, but I find this really hard. I prefer a different approach. There is a simple trick here, write your quality content, then use a
keyword density tool to find the keyword density. THEN, take the top words and add them to the meta keywords tag for that page. This is somewhat backwards for some maybe, it optimizes a page for what you actually wrote, rather than trying to write a page optimized for certain words. I find I get much better correlation like this and can then tweak my text afterwards.
Sure, if you want to you can further optimize by having the keywords in header tags and bold etc. As a guide, these might contribute only a few percent to the SERP

4. Accessibility of Document
“Accessibility is anything on the page that impedes a search engine
spider’s ability to crawl a page. There can be a number of
culprits:”

• Avoid Splash Pages: Flash and heavily graphic introductions prohibit engines from crawling your site.
• Avoid Frames: Never use pages with frames. Frames are too complex for the crawlers and too cumbersome to index.
• Avoid Cookies: Never require cookies for Web site access! Search engine crawlers are unable to enter any cookierequired materials.
• Avoid JavaScript when Possible: Though JavaScript menus are very popular, they disable crawlers from accessing those links. Most, well-indexed Web sites incorporate textbased
links primarily because they are search engine friendly. If necessary, JavaScript should be referenced externally.
• Avoid Redirects: Search engines frown upon companies that use numerous Web sites to redirect to a single Website.
• Avoid Internal Dynamic URLs on the Home page: Though many sites incorporate internal dynamic links, they should not incorporate those links on the home page. Engine crawlers are currently ill-equipped to navigate dynamic links - which often pass numerous parameters using
excessive characters.
• Utilize Your Error Pages: Too often companies forget about error pages (such as 404 errors). Error pages should always re-direct "lost" users to valuable, text-based pages.
Placing text links to major site pages is an excellent practice. Visit www.cnet.com/error for an example of a well-utilized error page.