CSS Form Validation Styles 2026 Clear validation feedback is critical for form UX. ProofMatcher's free form templates include validation styles — error borders, success indicators, and inline messages using pure CSS. CSS Error State .field { position:relative; margin-bottom:20px; } .field input { width:100%; background:rgba(255,255,255,0.06); border:1px solid rgba(255,255,255,0.12); border-radius:8px; padding:12px 14px; color:#fff; font-size:14px; outline:none; transition:border-color .2s; } .fi