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CSS Property:
border-image-width:
10%
20%
40%
30% 10%
30% 20%
30% 30%
20% 30%
10% 30%
30% 30% 10%
30% 30% 40%
30% 30% 40% 10%
30% 30% 40% 20%
Result:

This is a DIV element that uses an image as a border.

CSS Code:

    div#main {
        background-color:lightgrey;
        border:30px solid transparent;
        border-image: url('border.png');
        border-image-slice: 30;
        border-image-width: 10%;
        border-image-outset: 0;
        border-image-repeat: round;
        width:200px;
        height:50px;
    }

Click the property values above to see the result
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