CSS -背景附件:固定不停止滚动(tumblr主题)

我正在为tumblr主题做一些编码，并遇到这个问题:"background attachment: fixed"不会阻止背景图像上下滚动;它仍然会随着内容移动

HTML

<div id="content">
    <div id="posts">
        posts...
    </div>
</div>

CSS

#content {
    background-image: url('{image:Background Image}');
    background-repeat: no-repeat;
    background-attachment: fixed;
    height: auto;
    width: calc(100% - 300px);
    float: right;
}

宽度也不起作用，但我被告知这就是固定的工作原理，我只是想修复这个事实，即图像仍然移动

 background-attachment: fixed !important;

<img id="image" src="source" />
<div id="content"></div>

#image {
    height: 100%;
    width: 100%;
    position: fixed; //to prevent scrolling
    z-index: -1; //sets z-index, which wasn't working in my previous setup
}
#content {
    background: transparent;
    position: absolute;
    z-index: 1;
}