http://i.firefoxchina.cn/html/badbrowser.html

<script>var userAgent = navigator.userAgent,agentReg = /MSIE [67]\.\d/,isIELowerVersion = agentReg.test(userAgent);if(isIELowerVersion){window.location.href = "http://www.mamicode.com/html/badbrowser.html";}</script>

火狐对IE6,IE7的处理方式值得学习