Background fill

Ive been reading about setting a background wallpaper, and several forums say this should work:-

	html {
		background: url(images/wallpaper.png) no-repeat center center fixed; 
		-webkit-background-size: cover;
		-moz-background-size: cover;
		-o-background-size: cover;
		background-size: cover;
    }

Select allOpen in new window

It seems to fill, but not when then webpage is maximized and when the window is re-sized the image is scaled so there are gaps when the aspect ratio wont match to fill the screen.

Is there any CSS I can use to fill completely fill the background no matter what the aspect ratio is or maximized?

Thank you