WebPlayer - website JavaScript two-way communication example. The goal here is to keep the website JS code handy. Untested.

WebsiteCommunication.cs

using UnityEngine;
using System.Collections;


public delegate void JSCallback (string value);


public class WebsiteCommunication
{
	public TextAsset stringRequest;
	
	
	public void RequestString (JSCallback callback, string prompt, string defaultValue = "")
	{
		if !(callback.Target is MonoBehaviour)
		{
			throw new System.ArgumentException ("Callback must be on a MonoBehaviour!");
		}
		
		string evalText =
			stringRequest.text.Replace (
				"%GO_NAME%", ((MonoBehaviour)callback.Target).gameObject.name
			).Replace (
				"%HANDLER_NAME", callback.Method.Name
			).Replace (
				"%PROMPT_STRING%", prompt
			).Replace (
				"%DEFAULT_VALUE%", defaultValue
			);
		
		Application.ExternalEval (evalText);
	}
}


/*
String request variable is populated with a reference to a text file asset containing
the following JS code:

GetUnity ().SendMessage ("%GO_NAME%", "%HANDLER_NAME%", prompt ("%PROMPT_STRING%", "%DEFAULT_VALUE%"));
*/


// Example usage:

private string playerName = "Nobody";

void Start ()
{
	GetComponent<WebsiteCommunication> ().RequestString (OnReceiveName, "What is your name?", playerName);
}


void OnReceiveName (string name)
{
	playerName = name;
}