IE6 can't get new content

[huang mingyou <therods@xxxxxxxxx>]

hello,list.
       I have a site and  10 squid server  with httpd-accelerator
mode. when I change the site's content,use mozilla accept the content
,will get the new content.but use the IE6,some time get new
content,sometime get old content,what is the reason.
                        hmy