解决方案：
①两个叠在一起的层
②用半透明的png（推荐）
背景透明但文字不透明
支持IE、Firefox、Chrome、Opera
<html>
<title>透明</title>
<head>
<style>
#container {
color: #154BA0;
background: #ff0000;
filter: Alpha(Opacity=10, Style=0);
opacity: 0.10;
position: absolute;
height: 200px;
width:500px;
z-index:20;
}
#text {
position: absolute;
height: 200px;
width:500px;
text-align:center;
z-index:30;
}
</style>
</head>
<body >
<div id="container"></div>
<div id="text">背景半透明但文字不透明</div>
</body>
</html>
<title>透明</title>
<head>
<style>
#container {
color: #154BA0;
background: #ff0000;
filter: Alpha(Opacity=10, Style=0);
opacity: 0.10;
position: absolute;
height: 200px;
width:500px;
z-index:20;
}
#text {
position: absolute;
height: 200px;
width:500px;
text-align:center;
z-index:30;
}
</style>
</head>
<body >
<div id="container"></div>
<div id="text">背景半透明但文字不透明</div>
</body>
</html>