Any changes around CSS between Confluence 5.10.8 and 6.1.3?

[Hisamitsu Koga]

We have upgrade Confluence Server 5.10.8 to 6.1.3 recently. After upgrade, CSS about Sidebar doesn't work (is broken). Is there any changes between 5.10.8 and 6.1.3 which affects this CSS break?

[Nic Brough -Adaptavist-]

Yes, there's a lot of changes.  But if your sidebar is broken, it's not Confluence itself doing it, it's something you have configured - either an add-on or a css/html customisation in your system.  Check for those and (temporarily) remove them to see what might be breaking it.