Visitors and search engines love content-rich web sites, but just having a lot of content on your web site is not enough. It all has to be relevant to a main topic with each page or section of the web site having a specific theme (And yes, this includes any resource or links pages the site may have). Each page should have its own topic and content should not stray to a different topic.
If you are promoting your graphic design business and have a page on business card design, stay on the topic and refrain from using a page title such as "Graphic Design company in Vancouver, Canada - business cards, logos, letterheads". Your want the business card design to be the most important key phrase.
There are two main reasons for content relevancy. The first is so that visitors have an easy time understanding the flow of your web site. Visitors who have to search through multiple pages to find the information they're looking for won't be visitors much longer. The average web site user takes about three seconds to decide whether or not stay on a site. A clear idea of what your site is about should be apparent immediately, followed by easy navigation to other pages that display further topics in more detail.
The second reason for keeping content relevant throughout your web site is for search engine algorithms. Keyword relevancy is an important part of search engine optimization. The more relevant your web site's content is for a specific term, the more likely the site is to show up near the top of search results for the term.
Keyword density is another big deal with search engines. There is an optimal ratio of key terms to the overall amount of text that must be used for search engine optimization purposes. The more unrelated terms that are used consistently throughout the content will bring down the percentage of more important keywords. Keyword density matters throughout an entire web site, not just on certain pages.
Other areas to keep an eye on are the contact page, about us page, and any other pages that you may not think are important to have optimized for search engines such as advertising info, privacy policy, etc. For instance, some web sites have pages devoted to reciprocal links. There's nothing wrong with them unless you link out to a lot of unrelated web sites. The keywords that are used in the anchor text and surrounding description text will detract from your overall site content if they are not related. Incoming links from unrelated sites are fine, but keep in mind that the links page counts as part of your web site as a whole.
Consider using a reciprocal links page as more of a resource for visitors instead of a long list of irrelevant sites. This not only appeases search engines but your visitors as well. And as mentioned before, both visitors and search engines should be kept in mind when creating web site content.