popup message when WebGL is disabled

[josefspr]

Popup message with link to online pdf instructions (will load it as media file in amazon)
To test could not disable chrome but can disable Safari and Firefox:
Safari: preference->privacy->allow WebGL
Firefoz: about:config -> webgl.disabled

[josefspr]

also found how to disable chrome from terminal cmd
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome -disable-webgl