我用page speed测试网站性能时，有提显示说页面图片没有设置缓存时间。
请问，如何设置与个html页面和图片的缓存时时间？
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原page speed提示：
The following resources are missing a cache expiration. Resources that do not specify an expiration may not be cached by browsers. Specify an expiration at least one month in the future for resources that should be cached, and an expiration in the past for resources that should not be cached:
google翻译：以下资源缺少一个缓存过期。资源不指定期限不得由浏览器缓存。在指定的，应缓存资源的未来到期至少一个月，并在过去的资源过期不应该缓存：
* http://www.kz27.com/images/20091024.jpg
* http://www.kz27.com/images/about.gif
* http://www.kz27.com/images/addsite.gif
* http://www.kz27.com/images/css.css
* http://www.kz27.com/images/detail_img.jpg
* http://www.kz27.com/images/foot-L.jpg
* http://www.kz27.com/images/foot-M.jpg
* http://www.kz27.com/images/foot-R.jpg
* http://www.kz27.com/images/gaiban.gif
.....(下面还有)
谢谢！
如何对xml内容数据进行比较
例如：
<?xml version='1.0' encoding='utf-8'?>
<TestLIST>
<PID>40</PID>
<TestName>深圳市</TestName>
......
