代码如下：
<html><br />
<head><br />
<title>Upload Image</title><br />
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"><br />
</head><br />
<body bgcolor="#FFFFFF" text="#000000"><br />
<form name="IUpload" action="upfile.<a href="http://www.chinaitpower.com/Dev/Web/Asp/index.html" target="_blank">asp</a>" method="post"><br />
<p><input type="file" name="picsrc" size="40" onchange="picshow.src=document.IUpload.picsrc.value"><br />
<input type="button" value="上载" onclick="detect()"></p></form><br />
<p><img name="picshow" src="http://51js.1000box.net/pics/face/19.gif" title="图像预览"></p><br />
</body><br />
</html><br />
<br />
<SCRIPT LANGUAGE="JavaScript"><br />
<!--<br />
function imgExceedSize(w,h){<br />
if(!document.IUpload.picsrc.value==""){<br />
if(picshow.width>w||picshow.height>h){<br />
alert("图像尺寸："+picshow.width+"X"+picshow.height+"。\\n图像尺寸过大！你只能上传尺寸为 "+w+"×"+h+"的图像，请重新浏览图片！");<br />
return true;<br />
}else{<br />
return false;<br />
}<br />
}else{<br />
return true;<br />
}<br />
}<br />
<br />
function detect(){<br />
var ok=imgExceedSize(50,50);<br />
if(ok){<br />
document.IUpload.reset();<br />
}else{<br />
document.IUpload.submit();<br />
}<br />
}<br />
<br />
//--><br />
</SCRIPT>
[Ctrl+A 全选 提示:你可先修改部分代码,再点运行代码]