keyword density was an important factor in how a page was ranked. Keyword density is the percentage of times a keyword or phrase appears on a web page compared to the total number of words on the page.

SEO means Search engine optimization and SEM means Search engine marketing. SEO Optimizing our site for search engine friendly. SEM optimizing our site for Search Engine Marketing in the sense of e-commerce, Online Marketing products selling and buying,trade.

Page rank is a method for being popular and more searchable website by specific keywords. Page rank is a patten of Google. Google update the page rank every 3 months.