This should be known as long as you set the Max-age or expires on the line. Here's how to set the method under Apache:
Generate to open
Code to copy code as follows
LoadModule Headers_module modules/mod_headers.so
And then write it down Under the. htaccess file.
Code to copy code as follows
<ifmodule mod_headers.c>
<filesmatch "\. (ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf) $" >
Header set Cache-control "max-age=604800, public"
</FilesMatch>
<filesmatch (www.111cn.net) "\. (xml|txt) $" >
Header set Cache-control "max-age=18000, public, must-revalidate"
</FilesMatch>
<filesmatch "\. (html|htm|php|shtml) $" >
Header set Cache-control "max-age=3600, Must-revalidate"
</FilesMatch>
</IfModule>
If you do not open the "mod_headers" module, and do not add "<ifmodule mod_headers.c>" criteria to judge, the site will be wrong!
Setting Max-age or expires is used to cache static files, increasing the load speed of the site
From:http://www.111cn.net/sys/windows/68259.htm
Apache hint does not set max-age or expires workaround