Preventing “double” borders in CSS

Question

Say I have two divs next to each other (take https://chrome.google.com/webstore/category/home as reference) with a border.

Is there a way (preferably a CSS trick) to

Answer 1

HTML:

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4

​CSS:

div {
    border: 1px solid #000;
    float: left;
}

div:nth-child(n+2) {
    margin-left: -1px;
}

Demo

Include ie9.js for IE8 support (it's very useful for all CSS selectors/pseudo-elements).