滑块背景图片未在iOS移动设备上显示？

Question

网站背景图片显示在所有其他设备上，例如笔记本电脑和android手机。但是不仅限于ios mobile。我什至将图片的尺寸调整为768 px * 365 px，但无法正常工作。

.bg-img {
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    z-index: -1;
    background-position: center;
    background-size: cover;
    background-attachment: fixed;
}

.bg-img .overlay {
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    opacity: .8;
    background: #1C1D21;
}

<!-- Background Image -->
		<!-- large device only -->
		<div class="visible-xl visible-lg visible-md hidden-sm hidden-xs">
			<div class="bg-img" style="background-image: url('./img/team/background-clouds-dark-957002.jpg');">
			<div class="overlay"></div>
			</div>
		</div>
		<!-- mobile only -->
		<div class="visible-xs visible-sm hidden-md hidden-lg hidden-xl">
			<div class="bg-img" style="background-image: url('./img/team/Smallsize.jpg');">
				<div class="overlay"></div>
			</div>
		</div>
		<!-- /Background Image -->

Answer 1

css取决于浏览器而不是os 请安装chrome进行测试。或将CSS用于单独的浏览器

 #urID{
        background:url("../images/bg.jpg") no-repeat scroll right top #000000;
        -o-background-size: cover;
        -moz-background-size: cover;
        -webkit-background-size:cover;
        background-size: cover;
    }