UA User-Agent：用户代理，它是一个特殊字符串头，使得服务器能够识别客户使用的操作系统及版本、CPU 类型、浏览器及版本、浏览器引擎、浏览器语言、浏览器插件等。
标准格式为： 浏览器标识 (操作系统标识; 加密等级标识; 浏览器语言) 渲染引擎标识 版本信息
一些常见的UA：
""" PC端： safari5.1–MAC User-Agent:Mozilla/5.0(Macintosh;U;IntelMacOSX10_6_8;en-us)AppleWebKit/534.50(KHTML,likeGecko)Version/5.1Safari/534.50 safari5.1–Windows User-Agent:Mozilla/5.0(Windows;U;WindowsNT6.1;en-us)AppleWebKit/534.50(KHTML,likeGecko)Version/5.1Safari/534.50 IE9.0 User-Agent:Mozilla/5.0(compatible;MSIE9.0;WindowsNT6.1;Trident/5.0; IE8.0 User-Agent:Mozilla/4.0(compatible;MSIE8.0;WindowsNT6.0;Trident/4.0) IE7.0 User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT6.0) IE6.0 User-Agent:Mozilla/4.0(compatible;MSIE6.0;WindowsNT5.1) Firefox4.0.1–MAC User-Agent:Mozilla/5.0(Macintosh;IntelMacOSX10.6;rv:2.0.1)Gecko/20100101Firefox/4.0.1 Firefox4.0.1–Windows User-Agent:Mozilla/5.0(WindowsNT6.1;rv:2.0.1)Gecko/20100101Firefox/4.0.1 Opera11.11–MAC User-Agent:Opera/9.80(Macintosh;IntelMacOSX10.6.8;U;en)Presto/2.8.131Version/11.11 Opera11.11–Windows User-Agent:Opera/9.80(WindowsNT6.1;U;en)Presto/2.8.131Version/11.11 Chrome17.0–MAC User-Agent:Mozilla/5.0(Macintosh;IntelMacOSX10_7_0)AppleWebKit/535.11(KHTML,likeGecko)Chrome/17.0.963.56Safari/535.11 傲游（Maxthon） User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT5.1;Maxthon2.0) 搜狗浏览器1.x User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT5.1;Trident/4.0;SE2.XMetaSr1.0;SE2.XMetaSr1.0;.NETCLR2.0.50727;SE2.XMetaSr1.0) 360浏览器 User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT5.1;360SE) Avant User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT5.1;AvantBrowser) GreenBrowser User-Agent:Mozilla/4.0(compatible;MSIE7.0;WindowsNT5.1) 移动设备端： safariiOS4.33–iPhone User-Agent:Mozilla/5.0(iPhone;U;CPUiPhoneOS4_3_3likeMacOSX;en-us)AppleWebKit/533.17.9(KHTML,likeGecko)Version/5.0.2Mobile/8J2Safari/6533.18.5 safariiOS4.33–iPodTouch User-Agent:Mozilla/5.0(iPod;U;CPUiPhoneOS4_3_3likeMacOSX;en-us)AppleWebKit/533.17.9(KHTML,likeGecko)Version/5.0.2Mobile/8J2Safari/6533.18.5 safariiOS4.33–iPad User-Agent:Mozilla/5.0(iPad;U;CPUOS4_3_3likeMacOSX;en-us)AppleWebKit/533.17.9(KHTML,likeGecko)Version/5.0.2Mobile/8J2Safari/6533.18.5 AndroidQQ浏览器Forandroid User-Agent:MQQBrowser/26Mozilla/5.0(Linux;U;Android2.3.7;zh-cn;MB200Build/GRJ22;CyanogenMod-7)AppleWebKit/533.1(KHTML,likeGecko)Version/4.0MobileSafari/533.1 AndroidOperaMobile User-Agent:Opera/9.80(Android2.3.4;Linux;OperaMobi/build-1107180945;U;en-GB)Presto/2.8.149Version/11.10 AndroidPadMotoXoom User-Agent:Mozilla/5.0(Linux;U;Android3.0;en-us;XoomBuild/HRI39)AppleWebKit/534.13(KHTML,likeGecko)Version/4.0Safari/534.13 """
