If your using Chrome or a 64bit Web browser, there's compatibility issues with the Unity Web player where they dont play nice together, I believe the Chrome issue can be fixed with permissions but I dont know enough to walk you through it. If you develop with Unity, make sure both your Unity and web player versions are up to date with each other as if both are not in sync you will get that issue. If you are using Firefox or Internet explorer you shouldn't have any issues.
Hopefully that gave you some insight, if not the best I can say is look it up as it is likely a browser compatibility issue with Unity's Web player.
why are so many online games like this, you go to try then you gotta register or you see that 404 error, are games being stolen or what. I'm sure it's a decent card game though.
i'm guessing your games are decent enough to play but just hard to find a match in all of your MP games so why should I tell my friends to play, they barely even work for me as is but good luck in the future.
 "Apocalypse Pluto"){kind=icon}
 "Deactivator"){kind=icon}
 "Mafia Warfare"){kind=icon}
 "Emboscada"){kind=icon}
 "Formula Karting FC"){kind=icon}
 "Delta Force"){kind=icon}
 "PandaVenture"){kind=icon}
 "Bad Luck Brian"){kind=icon}
 "New Style Muscle Car"){kind=icon}
 "All That Matters"){kind=icon}
 "Cube House"){kind=icon}
 "Mafia Warfare - Online Collectible Card Game"){kind=icon}
 "Last Stand v2"){kind=icon}
 "Miscrits"){kind=icon}
 "Z Survival"){kind=icon}
 "Alien Defence"){kind=icon}
 "prototype"){kind=icon}
 "TacForce Alpha"){kind=icon}
 "The Way Of The Samurai"){kind=icon}
 "Lycans & Vampires - BETA"){kind=icon}
If your using Chrome or a 64bit Web browser, there's compatibility issues with the Unity Web player where they dont play nice together, I believe the Chrome issue can be fixed with permissions but I dont know enough to walk you through it. If you develop with Unity, make sure both your Unity and web player versions are up to date with each other as if both are not in sync you will get that issue. If you are using Firefox or Internet explorer you shouldn't have any issues. Hopefully that gave you some insight, if not the best I can say is look it up as it is likely a browser compatibility issue with Unity's Web player.