my suggestion would not to use the border properties, however create background image with the affect you are looking for and assign it to the body, making sure to provide an html color similar to the primary color of the image in-case the image for some reason doesn't show up
Code:
body {
background: #hexadecimal url('/path/to/image.ext');
}
than have a containing element for the content, and apply some the appropriate margin you wish to achieve, and assign a background color to distinguish the element from the desired body background.
HTML Code:
<body>
<div id="container">
<!-- body content here -->
</div>
</body>
Code:
div#container {
margin: 20px;
background-color: #ffffff; /* hexadecimal for white */
}
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