Links are an essential tool of search engine optimization. As more and more search engines adopt link popularity as an important aspect of their ranking algorithm, they also work to increase their ability to determine the value of links. By carefully crafting the text that you use to link internally and externally as well as any text that might accompany a link request, you can have a significant impact on the optimization of your web site.
Including keyword phrases in linked text helps improve not only the keyword density of your page, it also helps boost the relevancy of the page you are linking to. Search engines read and index the text used to describe a link and apply that text toward both the linker and the linkee's ranking.
For this reason, using your keywords in a link like so:
About Web Search
is much more effective than simply making the URL (which rarely contain keywords) the link text, as shown here:
http://websearch.about.com
In addition, some search engines will read and index the content of the title tag within an <> tag. Apart from the SEO value, this feature provides added usefulness for site visitors as the title tag is used to give further detail
about the page or content that a link refers to.
http://www.acmearticles.com/Article/Importance-of-relevant-links/13085
