Originally Posted by corona
I'm using 7zip as and archive manager. When it comes to deleting that pesky .css file, 7zip just opens the *.epub file as an archive and then you just close it. No renaming or anything needed. 7zip is open-source:
The CSS is not pesky and should not be deleted. The problem is not the CSS but bugs in the Kobo reader. Deleting the CSS can cause your ePub to look awful instead of formatted.