I have a master of IT, and I can say that I know a lot of skills related to IT especially Web. And I am thinking to operate my own business like providing hosting service, web design, etc and if possible, I wanna create a new social network site (for my own country). One of many obvious obstacles is how to start the business, from which point? Really, I don’t have any background on business or marketing. I think I need to learn more but which degree fits to solve my problem? As you know many degree related to business, but which one is the best for me?
Please don’t give me a trash. Thank you.

Succesful business owners don’t have degrees. Perhaps you are planing to own a business and let others run it? IN that case you just need money or access to it.
Digg.com is run by Kevin Rose and he built it while working on “The Screen Savers”
from wiki:
When Rose was starting Digg, he invested $6000 into the site, which was supposed to be for a deposit on a house for him and his girlfriend.
That’s how successful people get that way.
So pick a niche you enjoy and that you feel is going to grow in the future and don’t listen to people who tell you it is a bad idea. No one ever became anything great listening to do nothing naysayers.
Good luck
Hi. For the type of business you wish to start, I would suggest a combination of business law and marketing.
Business Law because of all the contractual agreements that will arrive from providing hosting and web design.
Marketing because it is the main ingredient in every field you wish to pursue. Please do not take offense to this, but you can have all the IT knowledge in the world, and be the best, but without successful marketing it is all for not in my opinion. This is especially true if you want to create your own social network site.