absolute是相对于最近定位祖先元素，relative相对于自身位置，fixed则相对于浏览器窗口固定定位。 1、 绘制两个方形。 2、 相对 ...

Why it matters: There are software flaws that tend to persist even in the most active projects. An open-source browser like Firefox, however, strives to be a true record-setter with decades-old bugs ...