How to create a full-page (cover) background image using CSS

Upload your background image onto your web server. I recommend a background photo of at least 1200px in width.

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

To add support for older versions of Internet Explorer, add the following lines:

filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='.myBackground.jpg', sizingMethod='scale');
-ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='myBackground.jpg', sizingMethod='scale')";

Once you've set the background image, check out this guide to learn how to attach a CSS stylesheet to an HTML document.