示例：
<iframe id="zyms" frameborder="0" scrolling="yes" style="width:1000px;"
onload=" this.height = 0;var fdh = (this.Document ? this.Document.body.scrollHeight : this.contentDocument.body.offsetHeight);
this.height = (fdh > 600 ? fdh : 600);"> </iframe>
原文：http://www.cnblogs.com/Dylanblogs/p/4330467.html