I was very frightened of losing the WYSIWYG interface and using gedit instead. But it is relatively simple to get a small site with simple functionality.
Some tips on coding here http://www.w3schools.com/html/default.asp
These are just the tutorials I Googled up and used. I don't know if there are any better ones.

It's actually quicker and easier to write your own Css and HTML files, rather than WYSIWYG, because when something goes wrong you can work out what it is and so troubleshooting is quicker.