<style type="text/css">

        .uploadWallpaperButton
        {
            height: 31px;
            width: 101px;
            cursor: pointer;
            margin: 5px;
            -moz-border-radius: 5px;
            -khtml-border-radius: 5px;
            -webkit-border-radius: 5px;
            border-radius: 5px;
            position: relative; background: url('pic.jpg') no-repeat;
        }
         .f
        {
            cursor: pointer;
            opacity: 0;
            filter: alpha(opacity=0);
            overflow: hidden;
            font-size: 90px;
            width: 101px;
            height: 31px;
        }
    </style>

<div title="上传壁纸..." class="uploadWallpaperButton upload" id="uploadWallpaperButton">
          <input type="file" name="pic"  class="f" id="imgfile" style="display: block;"/>
   </div>

修改后：