save html-formatted text to database

Try using htmlspecialchars() on the string to put into the DB, and then, when pulling it back out, use htmlspecialchars_decode(). Might make a difference.

Save it to a nvarchar(max) field.

Make sure you use parameterized queries for security. Read

http://www.aspnet101.com/2007/03/parameterized-queries-in-asp-net/

http://msdn.microsoft.com/msdnmag/issues/04/09/SQLInjection/

with little changes to Sql , you can apply to Mysql aslo