Background image into the entire webpage

Hello!

To fill the whole background of our forum, i used this short piece of CSS code:

.pageContainer, .pageHeaderContainer, body{
        background-image: url(#{$style_image_path}pageBG.jpg);    
        background-size: cover;
        background-repeat: no-repeat;
        background-attachment: fixed;
        margin:auto;
}

It looks to be working perfectly. However, i realized that in some mobile devices it isn't displaying correctly. Any tips to solve this problem? It's actually my 1st contact with CSS, so i believe my code could not be the most appropriate.

Thank you!
Kindly,
Paulo Almeida

Well it's hard to explain, because when i test on the browser with multiple devices, it's indeed displaying correctly.
But here is an example, how it appears on my cell phone. If the intention is impress through a good design, this end up to screw the page.

https://media.discordapp.net/a….jpg?width=381&height=676