Originally Posted by MrB
Thank you both for your replies. Being a complete beginner I hadn't realsied the significance of the big green tick in the Sigil tool-bar. I'm guessing that when I click that I'll be presented with further insights into the depths of my ignorance.
Who knew self-publishing could be such fun?
That Big Green Tick
does not check a CSS (or even if your code calls on a non-existent selector).
To Validate your CSS, you can use http://jigsaw.w3.org/css-validator
or Free CSS Toolbox
(Link not supplied as the installer adds many Ad
links to your start menu. Appears to be benign and removable, just annoying.