This example uses cssSandpaper to manipulate the gradient property. IE9 uses the Gradient Visual Filter to polyfill -sand-gradient() because don't work well at all in IE9 using the canvas polyfill. This is done by making the <body> tag a member of the CSS class cssSandpaper-IEuseGradientFilter Back to User Agent Man CSS3 Animation article
Just keep looking at this space. You'll see the colours in this box will be gradually changing. No, it isn't the mushrooms you had in the omlette this morning. It's cssSandpaper that is doing this. Don't be alarmed. Keep calm and carry on.