Similar to website ads, when we click to close it disappears, but we refresh the page again, it will reappear!
Essence: Let an element be hidden or displayed on the page.
display show hide
display: none ；隐藏对象
display：block ；除了转换为块级元素之外，同时还有显示元素的意思
After the display hides the element, it no longer occupies the original position.
The latter is widely used, and it can do a lot of webpage special effects with JS.
visibility show hide
visibility：visible ; 元素可视
visibility：hidden; 元素隐藏
After visibility hides the element, it continues to occupy the original position.
overflow overflow display hide
If there is a positioning box, please use overflow: hidden carefully because it will hide the extra part.
Tudou Mouse passing display mask
When the mouse passes: When the
mouse does not pass:
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<style>
.box {
position: relative;
width: 444px;
height: 320px;
background-color: pink;
margin: 30px auto;
}
.box img {
width: 100%;
height: 100%;
}
.mask {
display: none;
position: absolute;
width: 100%;
height: 100%;
background: rgba(0, 0, 0, .4) url(btn.png) no-repeat center;
}
/* 不能这样写，因为mask被隐藏了不占位置（自己的猜测 但是用visible好像也不行啊）
.mask:hover {
display: block;
} */
/* 当我们鼠标经过了这个盒子，就让里面遮罩层显示出来 */
.box:hover .mask {
display: block;
}
</style>
<body>
<div class="box">
<div class="mask"></div>
<img src="pic.jpg" alt="图片">
</div>
</body>
</html>