Theme incompatibility for upgrading to 4.6.11

[Philooo]

SInce years that I run the IPB system I had no problem with upgrades. I recently updated my server to PHP 8.0 but I had no problem with precedent upgrade.

But this week, when I want to run the 4.6.11 version, it blocks telling me that there is a "theme incompatibility"

I am blocked, I don't know what to do, what is the risk to continue, is there a roll back possibility 

many thanks in advance for your advice / help

[Jim M]

This is simply a warning to say that this file has been modified and our system is going to overwrite it. Core CSS files cannot be modified and will be overwritten between upgrades. If you're OK with that, you can proceed. If you are not then you will want to move your CSS edits to your own custom.css file as this is where customizations belong for CSS.

[Philooo]

Thank you JIM

I ran the 4.6.11 upgrade bypassing the them warning and all went nice
I do not see noticeable change in the theme

Thanks a lot !

[Jim M]

Glad to hear it went well 👍