作SEO时，我们经常会在日志上看到类似这样的代码：61.135.166.232 - - [31/Dec/2007:02:30:11 +0800] "GET /category21.html HTTP/1.1" 200 10968 "-" "Baiduspider+(+http://www.baidu.com/search/spider.htm)"66.249.70.172 - - [31/De...