css background height 100 width scroll

 

 

 

 

background-attachment: scroll CSS Background size.height:100 width:100 overflow:auto background:FF2400 opacity:0.2 You can use the above HTML code for using this CSS code. My header is 100 of the page width, when I expect it to be 100 of its parent width. The background appears at 100 of the window height, but it then scrolls up with the content. I would appreciate any help in understanding how CSS treats the 100 value in these two cases. right