使用YSlow发现所在服务器上传输出来的文件Expires头都置为Expires: Thu, 19 Nov 1981 08:52:00 GMT了，非常奇怪的一个时间（莫非apache或者php某个开发人员是这个时候出生的），YSlow给出了加载expires模块的建议。

加载expires模块之后，编辑httpd.conf加入如下配置：

# enable expirations
ExpiresActive On
# expire GIF images after a day from the time they were accessed
ExpiresByType image/gif image/jpg A86400
# HTML documents are good for a hour from the  the time they were accessed
ExpiresByType text/html M3600
# expire all default from the time they were accessed
ExpiresDefault “A7200″

今天下载了Yahoo的给Firefox开发的YSlow插件，这个插件确实不错，能够给出不少优化建议，发现所在主机没有开启deflate压缩。

首先加载mod_deflate。

在httpd.conf中加入

<Location />

# Insert filter
SetOutputFilter DEFLATE

# Netscape 4.x has some problems…
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip

# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won’t work. You can use the following
# workaround to get the desired effect:
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html

# Don’t compress images
SetEnvIfNoCase Request_URI .(?:gif|jpe?g|png|exe|bmp|mp3|rar|zip|swf|cab|t?gz|bz2|sit)$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.pdf$ no-gzip dont-vary

# Make sure proxies don’t deliver the wrong content
Header append Vary User-Agent env=!dont-vary

</Location>

再重启apache即可，/etc/init.d/apache2 restart

经过port80software的在线检测，首页大小从91977 bytes压缩到13376 bytes，传输速度提高6.8X，传输速度从原来12.832 s缩减到1.866 s。

如果修改配置之后提示“Invalid command ‘Header’, perhaps mis-spelled or defined by a module not included in the server configuration”，则加载Header模块即可，不过最好还是在编译apache模块时直接加上–enable-deflate –enable-headers就省事多了。