css中的四个不同的position设置
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
/* Positioning */
css 的 position 属性是用来设置元素的位置的,它还能设置一个元素出现在另一个元素的下层 元素能用 top,bottom,left 和 right 属性设置位置, 但是在默认情况下是不管用的,除非先设置了position属性 HTML 元素的位置默认是设置为静态(static)的, 位置设置为静态的元素的位置通常是根据正常的页面流向(flow)设置的 位置为静态的元素是不能被 top,bottom,left,right 影响的 共有四个不同的position设置方法 1.fixed 采用fixed position 的元素位置的设置相对于浏览器窗口 An element with fixed position is positioned relative to the browser window. 窗口滚动它也不会移动 It will not move even if the window is scrolled: 2.relative 相对位置指的是相对于它自己正常的位置 3.absolute 相对于第一个(紧包着的,最里层的)父元素 An absolute position element is positioned relative to the first parent element that has a position other than static. If no such element is found, the containing block is <html>: 4.overlapping 通过设置 position 和 z-index
* {
margin: 0px;
/*padding: 0px;*/
}
.pos_fixed {
position: relative; /*A relative positioned element is positioned relative to its normal position.*/
left: 10px;
top:10px;
width: 100px;
height: 100px;
border: 1px solid seagreen;
}
h2.pos_left {
position: relative;
left: -20px;
border: 1px solid crimson;
}
h2.pos_right {
position: relative;
left: 20px;
border: 1px solid crimson;
}
</style>
</head>
<body>
<div class="pos_fixed">
hello everyone.
</div>
<h2>This is a heading with no position</h2>
<h2 class="pos_left">This heading is moved left according to its normal position</h2>
<h2 class="pos_right">This heading is moved right according to its normal position</h2>
<p>Relative positioning moves an element RELATIVE to its original position.</p>
<!--<progress>progress</progress>-->
</body>
</html>