自定义文件上传框的样式

<script>
function fclick(obj){
  with(obj){
    style.posTop=event.srcElement.offsetTop
    var x=event.x-offsetWidth/2
    if(x<event.srcElement.offsetLeft)x=event.srcElement.offsetLeft
    if(x>event.srcElement.offsetLeft+event.srcElement.offsetWidth-offsetWidth)x=event.srcElement.offsetLeft+event.srcElement.offsetWidth-offsetWidth
    style.posLeft=x
  }
}
</script>
<style>
input{border:1px solid #333333;color:#666666;background:#eeeeee;font:normal 12px Tahoma;height:18px}
</style>
<form method="post" action="" enctype="multipart/form-data">
<input id="f_file">&nbsp;<input type="button" onmouseover="fclick(t_file)" value="选择上传文件">
<input name="upload" type="file" style="position:absolute;filter:alpha(opacity=30);width:30px;" id="t_file" onchange="f_file.value=this.value" hidefocus>
<br><input type="submit" value="提交">
</form>