Another way that decietful webmasters will trade links that are useless to your site is by mis-using the ROBOTS meta tag.
The ROBOTS meta tag tells a Search Engine whether to include that page in it’s index or not. The reason for this is that often times webmasters don’t want certain pages to be indexed, like password protected pages, etc. Some web masters will use the ROBOTS meta tag to keep their links page from being indexed, thus keeping the link to your site from counting. This is done by including the following line in the head section of the HTML code:
< meta name="ROBOTS" content="NOINDEX,NOFOLLOW" />
Do not exchange links with a site that does this. Because the page is not indexed, it should not receive Page Rank® of it’s own from the Search Engine. A link from this page is of no value to your website, because the Search Engines don’t count it as a link.