Where is the file for custom CSS?

I had the same error problem described in the thread below. I thought that the problem came from Adventurous Pro and re-installed but lost my custom CCS to reduce padding in the page and in the right hand column. Logged out of customization: https://catchthemes.com/support-forum/topic/big-problem-site-is-live-now-but-i-do-anything-under-customize/ I did a back up before re-installing. In what file can I find this custom CSS? Thanks for your help Julien PS: It seems like my hosting took off all the www. from all my domains.