<!DOCTYPE html>
<style>
.test {
    margin-top: 10px;
    width: 40px;
    height:40px;
    background-color: green;
}
</style>
https://code.google.com/p/chromium/issues/detail?id=321295
The top and bottom margins of a box collapse together only if they are the  "top and bottom margins of a box that does not establish a new block formatting context".
<br>
There should be no red below.
<div class="test"></div>