css 页面滚动 多背景固定不动
经常看到一些网站，滚动页面但是背景图不会跟着滚动，好像一直固定在浏览器窗口，感觉挺酷的，哇哦 ~ ~
原来都是 background-attachment 这位大兄弟的功劳
background-attachment：需要配合background-image一起使用
scroll：默认值，背景随内容滚动而滚动
fixed：背景固定不动，不受内容滚动影响
直接上代码，哇哈哈哈 ~ ~
<style>
.txt{
width: 100%;
height: 1000px;
text-align:center;
}
.bg1, .bg2, .bg3, .bg4{
width: 100%;
height: 400px;
background-size: cover;
background-attachment: fixed;
text-align: center;
color: #fff;
background-position: center center;
background-repeat: no-repeat;
}
.bg1{ background-image: url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1536819591022&di=fcf314d0fbb32a96d67dc015ee642734&imgtype=0&src=http%3A%2F%2Fold.bz55.com%2Fuploads%2Fallimg%2F141218%2F139-14121Q05415.jpg); }
.bg2{ background-image: url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1536819612013&di=5c21265ec22ca18b9f97459b0ffb5989&imgtype=0&src=http%3A%2F%2Fpic1.win4000.com%2Fwallpaper%2F6%2F5860a7fd794c2.jpg); }
.bg3{ background-image: url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1536819626165&di=0e6a7e49f95c3030848ba38e6333a983&imgtype=0&src=http%3A%2F%2Fimg5q.duitang.com%2Fuploads%2Fitem%2F201312%2F27%2F20131227233228_tLBH3.jpeg); }
.bg4{ background-image: url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1536819591022&di=fcf314d0fbb32a96d67dc015ee642734&imgtype=0&src=http%3A%2F%2Fold.bz55.com%2Fuploads%2Fallimg%2F141218%2F139-14121Q05415.jpg); }
</style>
<div class="txt">永远相信美好的事情即将发生</div>
<div class="bg1">原来就是这么简单哦</div>
<div class="txt">永远相信美好的事情即将发生</div>
<div class="bg2">原来就是这么简单哦</div>
<div class="txt">永远相信美好的事情即将发生</div>
<div class="bg3">原来就是这么简单哦</div>
<div class="txt">永远相信美好的事情即将发生</div>
<div class="bg3">原来就是这么简单哦</div>
