Links and content are both extremely important aspects when it comes to search engine optimization. If you wish to have your site be a success in the eyes of the search engines, you must have a strong combination of quality links coming to your web site as well as having quality content on your site.
When it comes to links you may notice many people and web sites placing great emphasis on link building and you may even come across web sites or emails offering you "amazing" text link deals.
You must be very careful of all paid text links for buying and selling links in order to effect search engine placement is against the conditions of every major search engine.
If you do decide to pursue links and are not aware of the value of a certain link, there is no guaranteed way to comprehend the full value of a link. Rather in most cases you must estimate the value and quite frankly no people will ever know the true value of a certain text link.