Table Salt can contain harmful carcinogens like talc and silica as well as Ferrocyanide which is an iron radical also found in blue dyes.
Whereas Sea Salt contains selenium that actually pulls harmful metals from your body, and creates an environment that resists bacteria and disease. It also contains Boron and Chromium which actually fight osteoporosis and help regulate blood sugar levels.
Resources
http://healthwyze.org/index.php/component/content/article/115-the-truth-about-table-salt-and-the-chemical-industry.html