css - opacity 属性有一些问题

Question

我希望我的 HTML 背景不透明度为 .9，但由于某些原因它不起作用。为什么会这样我真的不明白...

CSS

html{
  background: url(http://img.pixland.uz/u841f174959.jpg
  ) no-repeat center center fixed;
  background-size: cover;
  opacity: 1; <!-- if i decrease opacity 1 to 0.9 it will become very small   -->
}

demo

Answer 1

Have a fiddle!

CSS

html,body{
  background: url(http://img.pixland.uz/u841f174959.jpg) no-repeat center center fixed;
   background-size: cover;
  opacity: 0.5;
  height: 100%;    
}