The differences between salts, or why cooks never use table salt for anything because it is really really gross.
This is taken from a column written by J. Scott Williams at the Hawaiian Times.
Kosher salt: Kosher salt is “pure” salt. It has no additives and thus gives the cleanest, truest flavor. Its large flakes make it ideal for coating meats and any topical application, but it is harder to dissolve in liquids than table salt. If you (and I strongly recommend doing so) substitute kosher for table salt in a recipe, use slightly more, as the flake form makes it measure a bit lighter by volume. A tablespoon of kosher salt is roughly equivalent to two teaspoons of table salt. This is a great example of why weight measurement is always best!
Table salt: Iodized or not, table salt contains additives which can alter the taste of cooked materials. It also dissolves very quickly, so using it as part of a dry rub or on a steak before broiling is wasted effort. Keep this stuff on the table, where it belongs. (Although I prefer kosher salt for the table, too.)
Sea salt: On my last trip to Central Market, the official Houston grocery temple, I encountered a French sea salt for which I could have paid almost $80 a pound. I demurred in favor of five pounds of dry-aged standing rib roast. Now, for high-line gourmet recipes, especially seafood, sea salt can be a must. However, due to its high content of minerals other than good old sodium chloride, it is most definitely not recommended for everyday cooking.