Ideally, you will have unique pages, with unique page titles and unique page meta descriptions . Google does not seem to use the meta description when ranking your page for specific keyword searches if not relevant and unless you are careful if you might end up just giving spammers free original text for their site and not yours once they scrape your descriptions and put the text in main content on their site. I don’t worry about meta keywords these days as Google and Bing say they either ignore them or use them as spam signals.
QUOTE: “Returning a code other than 404 or 410 for a non-existent page (or redirecting users to another page, such as the homepage, instead of returning a 404) can be problematic. Firstly, it tells search engines that there’s a real page at that URL. As a result, that URL may be crawled and its content indexed. Because of the time Googlebot spends on non-existent pages, your unique URLs may not be discovered as quickly or visited as frequently and your site’s crawl coverage may be impacted (also, you probably don’t want your site to rank well for the search query” GOOGLE
In 1998, two graduate students at Stanford University, Larry Page and Sergey Brin, developed "Backrub", a search engine that relied on a mathematical algorithm to rate the prominence of web pages. The number calculated by the algorithm, PageRank, is a function of the quantity and strength of inbound links. PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfs the web, and follows links from one page to another. In effect, this means that some links are stronger than others, as a higher PageRank page is more likely to be reached by the random web surfer.
QUOTE: “So sites that don’t have much content “above-the-fold” can be affected by this change. If you click on a website and the part of the website you see first either doesn’t have a lot of visible content above-the-fold or dedicates a large fraction of the site’s initial screen real estate to ads, that’s not a very good user experience.” Google 2012
Basically, SEO keyword research should be an ongoing and ever-evolving part of your job as a marketer. Old keywords need to be reevaluated periodically, and high-volume, competitive keywords (or “head” keywords, as opposed to long-tailed keywords) can often be usefully replaced or augmented with longer, more specific phrases designed not to bring in just any visitor but exactly the right visitors. (Who visits your site – particularly if they’re people who are actively looking for your services – is at least as important as how many people visit.)