When Confluence is running behind Apache through mod_proxy, resources (such as the ui.css file) are not loaded correctly as it does not use the Base Server URL but instead the local URL (between Apache and Confluence).

Here are some example settings:

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

ProxyPass / http://localhost:8080/
ProxyPassReverse / http://localhost:8080/

The current workaround for Apache 2.x is using the following setting:

ProxyPreserveHost On

This issue is not present in previous versions of Confluence