blurry edge backgrounds by css

This is a question about the rendering quality of css gradient backgrounds.

I was going to use this free holding page template:
http://www.websuccessagency.com/in/coming-soon-demo/blue-horizons-3/
but when I saw that it was all images I thought maybe I would just
quickly copy it but code it better with css so that I could have it
fluid and responsive. Started by doing the blue and grey solid colours
of the background by using css 'gradients' and wrote

html{
background:...

blurry edge backgrounds by css