Here's a good explanation of the problems that can arise from having links to "http://www.seo-search-engine-ranking.com/" and "http://seo-search-engine-ranking.com/".
The problem arises because search engines think they're looking at different URLs and therefore different sites. Most webmasters can use a .htaccess file to solve the problem. It's all here.
Posted by James Trotta at February 27, 2004 5:25 PMThis article about links with www and without www is very informative. A lot of people wonder why google shows different pagerank for http://domain.com and http://www.domain.com.
Posted by: shahid at March 13, 2004 8:18 AMTrade links with seo-search-engine-ranking.com
http://www.seo-search-engine-ranking.com/ad_network_222.php