A shortcode is a tag like [authoravatars] which you can insert into a page or post to display a list of users on that post/page. You can read more about shortcodes in general in the wordpress codex, for example here or here.
As of version 0.6 the plugin comes with a tinymce plugin which makes it very easy to insert shortcode(s).
If you'd like to do it manually it's still simple: just add [authoravatars] into your post and hit save! There's a large number of parameters available.
The plugin comes with two shortcodes: [authoravatars] for lists of avatars and [show_avatar] for single avatars.
Make sure you have enabled the "blog filter" in Site Admin / Author Avatars for the blog on which you are trying to use this feature on. By default this is only enabled for the root blog (blog id = 1).
And you are running Wordpress MU, right?
No, the Author Avatars List plugin only provides ways of displaying user avatars.
The plugin uses the Wordpress Core Template function get_avatar() to retrieve the actual avatar images. In order to display custom images you need to look for plugins which use/override WordPress' avatar features and provide respective upload features...
Have a look at the User Photo Plugin (turn on option "Override Avatar with User Photo") or the Add Local Avatar Plugin.
This can happens when you've choosen to link users to their "author page" and the user has not written any posts on a blog. There are two things that you should do in this situation:
To prevent the 404 page from showing up install the Show authors without posts Plugin. This forces WordPress to always show the user page if the user exists.
If not already there add a custom user/author template to your theme. Otherwise if a user has no posts their user page is going to be quite empty by default... You can find a tutorial on Author Templates as well as a Sample Template File in the WordPress Codex.
The styling of the widget is controlled by the styles defined in css/widgets.css, avatars on posts/pages (using the shortcode) are styled by code in css/shortcode.css.
You can override the styles in that file by copying a style block to your theme's style.css and adjusting respectively. For example add the following to remove the padding from avatars displayed in a widget:
html .multiwidget_author_avatars .author-list .user {
padding: 0;
}




