像网易的云课堂那样浏览器低于某一版本就转到错误页面，用if lt IE 8之类的能实现么
回复讨论(解决方案)
js检测useragent来判断客户端浏览器版本
例如，检测IE
if (/MSIE (\d+\.\d+);/.test(navigator.userAgent)){ //test for MSIE x.x; var ieversion=new Number(RegExp.$1) // capture x.x portion and store as a number if (ieversion>=9) document.write("You're using IE9 or above") else if (ieversion>=8) document.write("You're using IE8 or above") else if (ieversion>=7) document.write("You're using IE7.x") else if (ieversion>=6) document.write("You're using IE6.x") else if (ieversion>=5) document.write("You're using IE5.x")}else document.write("n/a")