Passing parameters to Unity from outside

Hello.

I'm trying to make Login system for my web game.

I have a following situation: a player logged in on my site and press a button Play. This button redirects the player to the game. How can i pass any info (account ID for example) to the game when the button Play is pressed?

 

http://docs.unity3d.com/Manual/UnityWebPlayerandbrowsercommunication.html