First, the middle level
(1) the line element to its parent element to text-align: center can;
(2) a bulk element, which is provided margin: 0 auto can;
(3) if the sub-element comprising float: left attribute; child element to make the middle level, the need to set the width of the parent element fit-content, and with the margin: 0 auto, as follows:
.parent{
width: -moz-fit-content;
width: -webkit-fit-content;
width:fit-content;
margin:0 auto;
}
PS: Fit-Content currently only supports Chrome and firefox
(4)flex(2012)
.son{
display:flex;
justify-content: center;
}
(5) flex (2009), the parent element display: box; box-pack: center; following settings:
.parent {
display: -webkit-box;
-webkit-box-orient: horizontal;
-webkit-box-pack: center;
display: -moz-box;
-moz-box-orient: horizontal;
-moz-box-pack: center;
display: -o-box;
-o-box-orient: horizontal;
-o-box-pack: center;
display: -ms-box;
-ms-box-orient: horizontal;
-ms-box-pack: center;
display: box;
box-orient: horizontal;
box-pack: center;
}
(6) use of the new CSS3 transform property, provided the following sub-elements:
.son{
position:absolute;
left:50%;
transform:translate(-50%,0);
}
(7) using absolute positioning mode, and a negative margin-left, subelement (fixed width) as follows:
.son{
position:absolute;
width:固定;
left:50%;
margin-left:-0.5宽度
}
(8)使用绝对定位方式, 以及left:0;right:0;margin:0 auto; 子元素(宽度固定)设置如下:
.son{
position:absolute;
width:固定;
left:0;
right:0;
margin:0 auto
}
二、垂直居中
(1)若元素是单行文本,则可设置line-height即可;
(2)若元素是行内块级元素,用display:inline-block;vertical-align:middl和一个伪元素让内容块垂直居中:
.parent:after,.son{
display:inline-block;
vertical-align:middle;
}
.parent:after{
content:'';
height:100%;
}
(3)元素高度不固定,可使用vertical-align:middle,但是只用父元素是th或者td时此方法才有效,所以为了使用vertical-align,需要设置父元素display:table,子元素display:table-cell;vertical- align:middle;
优点:元素高度可以动态改变,不需在css中定义,如果父元素没有足够空间,该元素内容也不会被截断
缺点:ie6~7甚至ie8beta中无效
(4)flex(2012)
.parent{
display:flex;
align-items:center
}
优点:1、元素块的宽高任意 2、可用于更复杂高级的布局技术中
缺点:1、ie9-不适应 2、需要浏览器前缀 3、渲染有一些问题
(5)flex(2009)