Confluence still uses an uninstalled theme's layout (eg. the font will still be the old plugin's font) as its site layout although the plugin has been uninstalled.

Steps to replicate:

1. Install a theme plugin
2. Set the theme as the Site Theme
3. Uninstall the theme
4. Confluence theme selection page (http://ConfluenceURL/admin/choosetheme.action) will report that the site is using the default theme. Warnings will be populating the log file:

   2009-03-10 16:11:26,659 WARN [http-8080-3] [atlassian.confluence.themes.DefaultThemeManager] extractTheme Unable to find configured theme module: com.atlassian.confluence.themes.classic:classic
    -- referer: http://localhost:8080/admin/console.action | url: /admin/choosetheme.action | userName: admin
   

Customers who used the Classic Theme as a site layout might encounter this warning after they have upgraded to Confluence 2.10.

The work around is to set Confluence site theme to other installed theme.