MSDN上有一篇很详细的文章

http://msdn.microsoft.com/zh-cn/library/ms972974.aspx

但是我用的是另一个：UrlRewritingNet控件。

它的使用方法很简单：

1.将UrlRewritingNet.UrlRewriter.dll拷到bin目录下。 下载

2.在web.config里进行相关的配置
<?xml version="1.0"?>
<configuration>
    <configSections>
        <section name="urlrewritingnet" requirePermission ="false" type="UrlRewritingNet.Configuration.UrlRewriteSection, UrlRewritingNet.UrlRewriter"/>
    </configSections>

    <urlrewritingnet rewriteOnlyVirtualUrls="true" contextItemsPrefix="QueryString" defaultPage = "default.aspx" defaultProvider="RegEx" xmlns="http://www.urlrewriting.net/schemas/config/2006/07" >
        <rewrites>
            <add name="Rewrite"   virtualUrl="^~/(.*)/Detail(.*).aspx"
                  rewriteUrlParameter="ExcludeFromClientQueryString"
                  destinationUrl="~/Default.aspx?type=$1&id=$2"
                  ignoreCase="true" />
        </rewrites>
    </urlrewritingnet>

    <appSettings/>
    <connectionStrings/>
    <system.web>
        <compilation debug="true"/>
        <authentication mode="Windows"/>
        <httpModules>
            <add name="UrlRewriteModule"
                  type="UrlRewritingNet.Web.UrlRewriteModule, UrlRewritingNet.UrlRewriter" />
        </httpModules>
    </system.web>
</configuration>
大功告成！关键的2步都在这了，至于涉及的正则表达式等其它方面我也不懂，靠Google了。