css div vertical and horizontal centering implementation_html/css_WEB-ITnose

For example, if you set the div below in HTML to be centered vertically and horizontally, then

<<strong>div </strong><strong>id=</strong><strong>"box"</strong>></<strong>div</strong>>

css Style

<strong>#box</strong>{    <strong>width</strong>: 300<strong>px</strong>;    <strong>height</strong>: 200<strong>px</strong>;    <strong>margin-left</strong>: -150<strong>px</strong>;//宽度的一半，很重要，不然不居中，会偏右    <strong>margin-top</strong>: -100<strong>px</strong>;//高度的一半    <strong>position</strong>: <strong>absolute</strong>;//绝对定位方式    <strong>top</strong>: 50%;    <strong>left</strong>: 50%;    <strong>background-color</strong>: <strong>aqua</strong>;//背景颜色，便于测试查看效果}