How do i create these borders in the middle?

I know how to generate rounded corners using images. But please have a look at the link :-

http://roundedbox.andreas-kalt.de/

The rounded corners on all four corners are all images, but my question is how are those borders开发者_开发问答 in the middle done? Those green color borders that surround the whole div.

The tutorial is given but it is German :(. Also i don't want to use Css3 like -webkit-border-radius etc as they are not yet supported in IE

Thanks in advance :)

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The whole thing is done with a 4 background images here is the css

roundbox-tr {
    margin:15px auto;
    padding:0;
    background:url("roundbox_tr.gif") no-repeat right top;
    width: 90%;
}

/* top-left corner and left side */
.roundbox-tl {
    margin:0;
    padding:0;
    background:   url("roundbox_tl.gif") no-repeat left top;
}

/* bottom-right corner and bottom side */
.roundbox-br {
    margin:0;
    padding:0;
    background:   url("roundbox_br.gif") no-repeat right bottom;
}

/* bottom-left corner */
.roundbox-bl {
    margin:0;
    padding:0;
    background:   url("roundbox_bl.gif") no-repeat left bottom;
}

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They are used images for border. Use firebug addons in mozilla and check that.