一个网页的加载速度，跟父请求和子请求都是有关系的。
（1）、子请求出现了如404或者500之类的错误，会严重影响整个网页的加载速度。
（2）、子请求的响应速度慢，也会影响网页的加载速度。
我们在fiddler中的statistics面板选项，可以清楚的看到每个http请求的响应时间。
在overall elapsed中能看到http响应返回需要的响应时间。
Request Count: 1 Bytes Sent: 785 (headers:785; body:0) Bytes Received: 896 (headers:799; body:97) ACTUAL PERFORMANCE -------------- ClientConnected: 17:08:44.612 ClientBeginRequest: 17:08:45.548 GotRequestHeaders: 17:08:45.548 ClientDoneRequest: 17:08:45.548 Determine Gateway: 0ms DNS Lookup: 0ms TCP/IP Connect: 0ms HTTPS Handshake: 0ms ServerConnected: 17:08:44.772 FiddlerBeginRequest: 17:08:45.548 ServerGotRequest: 17:08:45.548 ServerBeginResponse: 17:08:45.648 GotResponseHeaders: 17:08:45.648 ServerDoneResponse: 17:08:45.648 ClientBeginResponse: 17:08:45.648 ClientDoneResponse: 17:08:45.648 Overall Elapsed: 0:00:00.100 RESPONSE BYTES (by Content-Type) -------------- ~headers~: 799 text/html: 97 ESTIMATED WORLDWIDE PERFORMANCE -------------- The following are VERY rough estimates of download times when hitting servers based in Seattle. US West Coast (Modem - 6KB/sec) RTT: 0.10s Elapsed: 0.10s Japan / Northern Europe (Modem) RTT: 0.15s Elapsed: 0.15s China (Modem) RTT: 0.45s Elapsed: 0.45s US West Coast (DSL - 30KB/sec) RTT: 0.10s Elapsed: 0.10s Japan / Northern Europe (DSL) RTT: 0.15s Elapsed: 0.15s China (DSL) RTT: 0.45s Elapsed: 0.45s ________________ Learn more about HTTP performance at http://fiddler2.com/r/?HTTPPERF
statistics面板选项：是一个详情和数据统计面板，显示了每条http请求的具体统计信息，如：发送、接收的字节数，发送、接收时间，
以及粗略的统计世界各地访问该服务器所花费的时间。