Strange borders inside ligtbox

Borders around image look fine. I see a white border above the close button. This is because the lightbox has the “button” tag for the close icon.
Your theme css, http://guncitychoppers.dk/wp-content/themes/vantage/style.css line 295 calls for a box shadow:

button, html input[type="button"], input[type="reset"], input[type="submit"]  {
 box-shadow: 0 1px 1px rgba(0, 0, 0, 0.125), 0 1px 0 rgba(255, 255, 255, 0.5) inset;
}

So in the light box css, http://guncitychoppers.dk/wp-content/plugins/lightbox-plus/css/black/colorbox.css you need to add ‘box-shadow:none’ to this style, so it’ll be:

#cboxClose {
    background: url("images/close.png") no-repeat scroll center top rgba(0, 0, 0, 0);
    bottom: -25px;
    box-shadow: none;
    display: block;
    height: 22px;
    position: absolute;
    right: 5px;
    text-indent: -9999px;
    width: 22px;
}