Do you depend on free search engine traffic for your livelihood?I admit it. I spend an inordinate amount of time thinking about Search Engine Marketing (SEM), Search Engine Optimization (SEO), keyword density, keyword relevance, KEI, incoming links and link text, and where my web site and web pages rank in the Search Engine Results Pages (SERP) for my targeted keyword phrases.This afternoon I had a shock. I discovered my main web site was dropped from Yahoo! Not one page could be found in Yah.