For those of you trying to speed up your website and using YSlow or Page Speed, you always get those:

The following cacheable resources have a short freshness lifetime. Specify an expiration at least one month in the future for the following resources: or
Grade F on Add Expires headers
Try adding the code below to your .htaccess file

<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/gif A2592000
ExpiresByType image/jpg A2592000
ExpiresByType image/png A2592000
ExpiresByType application/x-javascript A2592000
ExpiresByType text/css A2592000
ExpiresByType image/x-icon A2592000
</IfModule>

This should help image, css and some java scripts. A2592000 = 720hours = 30days
the numbers after A is the time to expire time (in seconds)
A3600 is 1 hour.
This does not help for google adsense java script or any other advertising java scripts. Unfortunately it is up to the script provider to make changes but we are still looking.

If you have any other solutions we would love to see you post it here.