CSS-背景附件 | background-attachment

/* Keyword values */
background-attachment: scroll;
background-attachment: fixed;
background-attachment: local;

/* Global values */
background-attachment: inherit;
background-attachment: initial;
background-attachment: unset;

<attachment>#where 
<attachment> = scroll | fixed | local

<p>
  There were doors all round the hall, but they were all locked; and when
  Alice had been all the way down one side and up the other, trying every
  door, she walked sadly down the middle, wondering how she was ever to
  get out again.
</p>

p {
  background-image: url("https://mdn.mozillademos.org/files/12057/starsolid.gif");
  background-attachment: fixed;
}

<p>
  There were doors all round the hall, but they were all locked; and when
  Alice had been all the way down one side and up the other, trying every
  door, she walked sadly down the middle, wondering how she was ever to
  get out again.

  Suddenly she came upon a little three-legged table, all made of solid
  glass; there was nothing on it except a tiny golden key, and Alice's
  first thought was that it might belong to one of the doors of the hall;
  but, alas! either the locks were too large, or the key was too small,
  but at any rate it would not open any of them. However, on the second
  time round, she came upon a low curtain she had not noticed before, and
  behind it was a little door about fifteen inches high: she tried the
  little golden key in the lock, and to her great delight it fitted!
</p>

p {
  background-image: url("https://mdn.mozillademos.org/files/12057/starsolid.gif"),
      url("https://mdn.mozillademos.org/files/12059/startransparent.gif");
  background-attachment: fixed, scroll;
  background-repeat: no-repeat, repeat-y;
}