css透明背景如何兼容各个浏览器

<div class="linkGroup linkGroup-25">
<div class="item">15天无理由退换</div>
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<div class="item">终身技术保修</div>
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</div>

.linkGroup{
&:after{
content: '';
display: block;
visibility: hidden;
height: 0;
clear: both;
}
>.item{
float: left;
}
&.linkGroup-25{
position: absolute;
left: 470px;
bottom: 46px;
>.item{
float: left;
width: 223px;
height: 75px;
line-height: 75px;
border-radius: 4px;
background-color: #000;
background-color: rgba(0,0,0,.7);
opacity:0.50;filter:alpha(opacity=50);
color: #FFFFFF;
border:1px solid #FFFFFF;
font-size: 22px;
text-align: center;
& + .item{
margin-left: 25px;
}
}
}
}

background-color: #000;
background-color: rgba(0,0,0,.7);
opacity:0.50;filter:alpha(opacity=50);