How to install unity web player on Ubuntu 14.04?

A solution could be to use Pipelight:

Here how to install Pipelight on Ubuntu: http://pipelight.net/cms/install/installation-ubuntu.html

sudo add-apt-repository ppa:pipelight/stable
sudo apt-get update
sudo apt-get install --install-recommends pipelight-multi
sudo pipelight-plugin --update

Here how to activate the Unity Web Player Plugin: http://wiki.unity3d.com/index.php/Running_Unity_Web_Player_on_Linux_using_Pipelight

#!/bin/bash

#FDS-Team: Pipelight Project
#Tomasz Zackiewicz, Pipelight.sh


#update the checksum of Unity3D Web Player
sudo pipelight-plugin --update

#for Firefox, clear the plugin cache
sudo pipelight-plugin --create-mozilla-plugins

#enabling Unity3D Web Player
sudo pipelight-plugin --enable unity3d