css控件透明属性设置IE firefor设置方法
<STYLE type=text/css>
.upfilefield{position:absolute; FILTER: alpha(opacity:0);-moz-opacity:0.5;opacity: 0; width:88px; height:29px; top:0px; right:0px;}
</STYLE>

导入：<input type="file" name="file" id="file" class="easyui-validatebox" data-options="required:true" style="position:absolute; FILTER: alpha(opacity:0);-moz-opacity:0.5;opacity: 0;width:150px;"/>
<input type="button" onclick="chooseFile()" value="http://www.mamicode.com/选择EXCEL表" style="border:none;" />

ie 设置为FILTER: alpha(opacity:0);
firefor 设置为-moz-opacity:0.5;opacity: 0; 

function chooseFile(){
document.getElementById("file").click();
}

css控制file控件透明 漂浮