I toyed with the idea of nesting elements with borders and some negative margins to pull one border on top of another, or nesting a border inside an outline and then using negative margins to keep from throwing off the layout. But none of that felt satisfying.
It turns out there are a number of tricks to create the effect of stacking one border atop another by combining a border with some other CSS effects, or even without actually requiring the use of any borders at all. Let’s explore, shall we?
That’s from the introduction to my article “Stacked ‘Borders’”, which marks the first time I’ve ever been published at the venerable upstart CSS-Tricks. (I’m old, so I can call things both venerable and an upstart. You kids today!) In it, I explore ways to simulate the effect of stacking multiple element borders atop on another, including combining box shadows and outlines, borders and backgrounds, and even using border images, which have a much wider support base than you might have realized.
And yes, as per my usual, the images in the piece are all double-dpi :screenshot captures directly from Firefox.
Many thanks to Chris Coyier for accepting the piece, and Geoff Graham for his editorial assistance. I hope you’ll find at least some part of it useful, or better still, interesting. Share and enjoy!