February 7, 2017 at 8:35 am #251110
If I understand correctly, you can create a basic form where you save the entered CSS to a file that just so happens to be a stylesheet referenced in the head of a web page. This should start you off http://fofwebdesign.co.uk/template/_testing/test/save-file/
Be aware – it’s extremely basic, so you should look into building on it with password protection and cleanse the data input before saving.
And for anything more complex – like a full-blown edit-in-place solution for more complex web pages – you should do as Paulie suggested and look into some sort of plugin.