Without relevance SEO is a lost cause, since search engines were abused with meta tags in the past, many of them omit this as a summary and rely on other ranking factors that are known to produce results.

Trust rank for example and phrase rank are new formulas in the algorithm that now take the place of keyword density. What this means in layman's terms is, if your pages do not share a particular theme, or have a certain thresh hold of related keywords, then they are essentially devalued as an attempt to inflate rankings.

Relatively any term can be optimized, with the right resources, a bit of patience and strategic positioning virtually any term can be associated and specified to correspond with a particular website. Usually, this requires a complete content management strategy, starting from developing an on topic topical theme of well written articles, references and information and web pages free of errors that can be crawled easily by spiders.

If client (a) wants to rank for a high volume term (go figure) however after the analysis you determine that the keyword density on the page is hardly enough to even be recognized in any way shape or form in relationship to their site.

Not only do you have to break it to them softly that in order to rank for specific terms, that should be the theme of the page, right? Sounds simple enough.The real catch is through either lack of preparation or simple oversight the real reason anyone wants to optimize any page is to get traffic, but what value is it once they arrive and find jibber-jabber or off-topic content?

My suggestion, pay attention to word density (the number of times a keyword appears on that page, title and description) but make sure that you really have something to say before you embark on the quest to bring the crux of the web to visit your website.

Nine times out of ten, if people would place more emphasis on the content they provide, their conversion rate from surfers who happen to breeze through vs. individuals who identified with the message on your page, found something useful or responded to something compelling enough to reach out and leave a comment, link to your site or purchase your products or services would most definitely increase.

In conclusion, it's not always about optimization, it's about retention and conversion through engaging the visitor to leave a lasting impression and build your online brand. In nutshell, it's not how many visitors your website gets, it's how many keep coming back.