While WordPress makes it easy for non-coders to manage a website, there will probably come a time when you want to edit code in WordPress to get a little more control over how your site looks or functions. Here are some beginner’s guides on how to edit HTML and CSS code, etc.
Beginner’s Guide for WordPress
HTML5 / CSS3
User Interface Design (UI) & User Experience (UX) Design
PHP (Hypertext Preprocessor)