A gravatar, or globally recognized avatar, is quite simply an 80×80 pixel avatar image that follows you from weblog to weblog appearing beside your name when you comment on gravatar enabled sites. Avatars help identify your posts on web forums, so why not on weblogs? More information about gravatars, please visit Gravatar.com.
The Gravatar plugin for Nucleus allows you to use gravatars on your Nucleus based blog. It's really simple to use. Install the plugin and include one little variable in one of your templates. That's all there is to it. Now gravatars will automatically appear to next to each comment of which the poster has registered with Gravatar.com.
Additional information is available on Rakaz' weblog.
The final step is to go to your templates and select the full template of the skin you are using, for example grey/full. Go to the Comments Body section. Then place the template var
<%Gravatar%> in the location you like. For example:
<h3 class="comment"><%Gravatar%> <%user%> wrote:</h3> <div class="commentbody"> <%body%> </div> <div class="commentinfo"> <%date%> <%time%> </div>
And your done! The gravatars should appear automatically.