Unity3D web player (plug-in)
You enter the 3D mall directly from your web browser. To enter the 3D mall for the first time you need to install a small browser plug-in.
Plug-in is safe to use and it doesn't take computer resources while it's out of usage.
Unity3D is available for Windows and Mac OSX.
To install a plug-in for your browser please download the Unity3D plug-in from the Unity3d website or using the link provided here and then install it.
For details on how to download and install a plug-in, check the videos below:
MAC - Safari:
Windows 7 - Internet explorer 8: