Background Image

Hey, How can I add a repeating background image. I have the image, but whenever I change it in style.css, nothing changes.

body {
	margin: 0;
	padding: 0;
	text-align: center;
	background: #f4f6da url('images/background.png') repeat fixed;
	color: #363636;
	font-family: Helvetica, Arial, sans-serif;
	font-size: 0.8em;
}

I want the background to be like https://www.press75.com/themes/side-blog-theme-demo/