does search engine calculate title tag, meta keyword, meta description, and all character at once while giving out keyword density?? and what is the optimum keyword density for a webpage?? plz guide through this
It's 4% maximum in one page. Yes Search Engine checks that "how many times you have used the same KW in a page?" so as to maintain the SPAM listings in Search Engine.
And you could even go a step further and drop to no larger than 2%. The recent EMD algo changes and associated changes that went along with it are complicated. Larger articles that are good, not to many kw's to a page and reasonable related kw density will win the day.