Is posible to create multiplayer game ON MY WEBSITE without having dedicated server?
I create this but others don’t see my server-room and can’t connect as client.
It still runs localy.
You could setup a free PhotonCloud account, that will allow for up to 20 players… Porting Unity networking code to photon networking is easy to do, most of the work is don’t automatically by it’s code porter…
If your game doesn’t require authoritative servers then cloud services like badumna and photon are there to help you.
If you code it properly using Unity’s built-in networking system then your game should work fine in the web player regardless of where the user downloads your game from - whether it’s a file on your disk, or a server on your LAN, or your public server on the Internet, ultimately your game runs on the player’s computer in pretty much the same state (there are differences for WWW and .NET socket access, but the built-in networking system is not affected).
You will need to enable NAT when you initialize the server, and be aware of all the problems with NAT, as most of your users will be behind NATs. Bear in mind that NAT punchthrough is sometimes impossible due to the users’ NAT configurations. So there are a few reasons why you might find it doesn’t work.
I found solution, i use Photon Cloud 
You are right , built in networking can be used for this and even when nat doesn’t work he can use a proxy server which becomes something like photon cloud or baduman which i recommended, The only difference is that he has to host the master server for proxy server functionality but cloud services doesn’t require hosting.
You can take a look at AppWarp cloud solution. It offers a realtime multiplayer gaming backend in which you don’t need your own dedicated server. Here is a link to the product page with a couple of Unity samples which illustrate the integration.
http://appwarp.shephertz.com/game-development-center/unity3d-game-developers-home/