是user-agent用于检测手机浏览器。有很多免费的脚本可以检查这一点。这里有一个这样的php代码，它将帮助你重定向移动用户到不同的网站。

有一个全新的解决方案使用Zend框架。从Zend_HTTP_UserAgent的链接开始:

http://framework.zend.com/manual/en/zend.http.html

Just a thought but what if you worked this problem from the opposite direction? Rather than determining which browsers are mobile why not determine which browsers are not? Then code your site to default to the mobile version and redirect to the standard version. There are two basic possibilities when looking at a mobile browser. Either it has javascript support or it doesn't. So if the browser does not have javascript support it will default to the mobile version. If it does have JavaScript support, check the screen size. Anything below a certain size will likely also be a mobile browser. Anything larger will get redirected to your standard layout. Then all you need to do is determine if the user with JavaScript disabled is mobile or not. According to the W3C the number of users with JavaScript disabled was about 5% and of those users most have turned it off which implies that they actually know what they are doing with a browser. Are they a large part of your audience? If not then don't worry about them. If so, whats the worst case scenario? You have those users browsing the mobile version of your site, and that's a good thing.

适用于安卓，IPHONE, IPAD，黑莓，PALM, WINDOWS CE, PALM

 <script language="javascript"> <!--
     var mobile = (/iphone|ipad|ipod|android|blackberry|mini|windows\sce|palm/i.test(navigator.userAgent.toLowerCase()));
              if (mobile) {
                  alert("MOBILE DEVICE DETECTED");
                  document.write("<b>------------------------------------------<br>")
                  document.write("<b>" + navigator.userAgent + "<br>")
                  document.write("<b>------------------------------------------<br>")
                  var userAgent = navigator.userAgent.toLowerCase();
                  if ((userAgent.search("android") > -1) && (userAgent.search("mobile") > -1))
                         document.write("<b> ANDROID MOBILE <br>")
                   else if ((userAgent.search("android") > -1) && !(userAgent.search("mobile") > -1))
                       document.write("<b> ANDROID TABLET <br>")
                   else if ((userAgent.search("blackberry") > -1))
                       document.write("<b> BLACKBERRY DEVICE <br>")
                   else if ((userAgent.search("iphone") > -1))
                       document.write("<b> IPHONE DEVICE <br>")              
                   else if ((userAgent.search("ipod") > -1))
                       document.write("<b> IPOD DEVICE <br>")
               else if ((userAgent.search("ipad") > -1))
                       document.write("<b> IPAD DEVICE <br>")
                       else
                   document.write("<b> UNKNOWN DEVICE <br>")
              }
              else
                  alert("NO MOBILE DEVICE DETECTED"); //--> </script>

在检测移动浏览器上有开源脚本，可以在Apache、ASP、ColdFusion、JavaScript和PHP中实现这一点。

可以检查User-Agent字符串。在JavaScript中，这很简单，它只是navigator对象的一个属性。

var useragent = navigator.userAgent;

你可以在JS中检查设备是iPhone还是黑莓

var isIphone = !!agent.match(/iPhone/i),
    isBlackberry = !!agent.match(/blackberry/i);

如果isIphone是真的，你是通过Iphone访问网站，如果是黑莓，你是通过黑莓访问网站。

你可以使用firefox的“UserAgent Switcher”插件来测试。

如果你也感兴趣，可能值得一试我的脚本“redirection_mobile.js”托管在github这里https://github.com/sebarmeli/JS-Redirection-Mobile-Site，你可以在我的一篇文章中阅读更多细节:

http://blog.sebarmeli.com/2010/11/02/how-to-redirect-your-site-to-a-mobile-version-through-javascript/