Please see the access.log below: # tail -f access.log |grep all.js|grep MISS 1203926657.352 189 222.136.187.144 TCP_MISS/200 27617 GET http://r14-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926657.750 114 221.11.92.130 TCP_MISS/200 27617 GET http://r14-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926658.696 988 221.3.235.6 TCP_MISS/200 27617 GET http://r14-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926660.663 352 211.97.118.168 TCP_MISS/200 12718 GET http://res-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926661.194 21606 221.11.16.110 TCP_MISS/200 68533 GET http://r14-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926662.414 1121 121.68.66.119 TCP_MISS/200 27617 GET http://res-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript 1203926663.557 1673 121.41.135.133 TCP_MISS/200 27617 GET http://res-js.mail.xxxx.com/zh_CN/htmledition20080131/js/all.js - FIRST_UP_PARENT/RES application/x-javascript Why there are so many MISS with FIRST_UP_PARENT reason? I'm running Squid-2.7 the current version for reverse-proxy. Thanks!