Use your own package name
com.atlassian.confluence.plugins.*. That is confusing to people who try to use the plugin. Use a real package name that corresponds to your organisation or project. For example:
org.mycompany.confluence.plugins.*. The Sun Java documentation has some tips about conventions used to ensure unique package names.
In the CSS realm, there is an official namespace proposal, but that's not what I'm talking about as the current browser crop doesn't support these enhancements yet. All I'm really talking about is intelligently naming your selectors so that you don't bleed styles between your plugin and the product itself. For example, rather than having an element like:
you might try
That will ensure that your CSS rules don't get applied to anyone else's plugins, and you don't inadvertently pick up a style from Confluence's table class that may change in the future.