We are not talking human accessibility here (as in 508). Accessibility is anything on the page that impedes a search egine spider’s abilty 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 cookie-required materials.
• Avoid JavaScript when Possible: Though JavaScript menus are very popular, they disable crawlers from accessing those links. Most, well-indexed Web sites incorporate text-based 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 Web site.

Wordtracker and other keyword research tools not only provide you with a potential list of keywords but also give information relating to the approximate number of searches conducted using that term. Ensure that your potential keywords do receive searches. Another useful piece of information is the number of pages that are displayed for that search term. You should try to find the perfect balance that ensures you aren’t competing with hundreds of millions of different pages but that the keyword does receive a reasonable number of searches every month.

Way, way back when that wall was still upright search engine algorithms were so dumb they couldn’t work out what a page was about just from the content. So some bright spark had the ingenious idea to create a set of tags (meta tags) that inferred information about a pages content to the search engines.

Great idea, except there was nothing to stop a webmaster stuffing or spamming their Meta Tags with irrelevant, but very high traffic keywords and keyword phrases. Which of course they did with enthusiasm, you would find adult sites using words like Disney and Pokemon in their Keywords Meta Tag for the traffic!!

It is the process of ranking a website on search engine page results (SERPS) with targeted and relevant keywords regarding your web site text-content. If your website is about widgets you surely want to appear in the TOP 10 SERPS when a visitor type 'widgets' in the search box of any search engines. Well you will find plenty of useful informations on how to reach that goal by reading the articles of this site!