Internet Explorer considers Silverlight as a kind of ActiveX control. So to find if Silverlight is installed, we can attempt to create this ActiveX control using
Javascript. If it fails to create the ActiveX control, we can assume that Silverlight is not installed.

For other browsers like Google Chrome, Netscape, FireFox, Safari etc, this can be determined by looking in to the Plugin array of the navigator object.
The Silverlight plugin is installed with the name 'Silverlight Plug-In'.

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