We've had a few complaints about this issue. Is there any update on this in the 3 months since CPANEL-33911 was logged?
From our own testing we've found the cPanel internal Apache(?) serving webmaild is changing the content of the bootstrap-cpanel.min.css file in the elastic skin directory when served.
The 'on the fly' editing changes quotation marks and double backslashes around any 'url(data...' entries in the bootstrap-cpanel.min.css file.
This appears to be the root cause of the .css issues (and transparency) in Elastic skin.
From our own testing we've found the cPanel internal Apache(?) serving webmaild is changing the content of the bootstrap-cpanel.min.css file in the elastic skin directory when served.
The 'on the fly' editing changes quotation marks and double backslashes around any 'url(data...' entries in the bootstrap-cpanel.min.css file.
This appears to be the root cause of the .css issues (and transparency) in Elastic skin.