A bit more complicated but useful option:
http://dabblet.com/gist/2884899
These are two elements of the brother, absolutely and relatively positioned, z-indexed to overflow one another. the top div hides the bottom top border of the div.
This is useful for drop down menus. (to have a frame with a frame, expand it using the context menu)
EDIT (code inserted from link):
HTML
<div class="holder"> <div class="top"></div> <div class="bottom"></div> </div>
CSS
.holder{ position:relative; } .top{ width: 50px; height:50px; background:red; border:blue solid 2px; border-bottom:none; position:relative; z-index:4; } .bottom{ z-index:2; width: 100px; height: 100px; position:absolute; top:50px; left:0; border: blue solid 2px; background:red;
}
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