未知尺寸的图片把页面撑破的简单解决办法

<script language="JavaScript" type="text/JavaScript">
function resizepic(thispic)
{
if(thispic.width>700) thispic.width=700;
}
</script>

<img src="http://www.google.com/intl/zh-CN_ALL/images/logo.gif" onload="if(this.width>200)this.width=200">

img {max-width: 500px; width:expression(this.width > 500 ? "500px" : this.width)}