**CSS Conventions** All markup is lowercase * All CSS-Classes need to be prefixed with "t3-" Example: t3-icon t3-icon-open * All CSS Classes are lowercase (existing CSS classes and IDs need to stay), and multiple parts must be separated with a dash ("-") Right: "t3-form-field" Wrong: "typo3-TCEFORMs-field" * Multiple CSS classes should be used, where the description makes sense and to be more specific t3-btn t3-btn- CSS classes are helpers for to address design and behaviour, data should be put in separate HTML5 data attributes Common usage .t3-btn .t3-container .t3-icon - icon sprites