By default, WordPress uses Gravatar icons for all user comments.
This means that for every commenting user, the site's server issues a request for the user's avatar, embedding it inside the page where it's needed.
NIX Gravatar Cache helps improve loading speed on pages with lots of comments.
It works by caching all Gravatar images locally, for a specified amount of time.
This means the server does not query for the same image every time the page is loaded and uses a locally stored copy instead.
Unpack and upload it to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.
· WordPress 3.0.1 or higher