<style> * { box-sizing: border-box; margin: 0; padding: 0; } body { width: 100%; height: 100vh; display: flex; justify-content: center; align-items: center; background: gainsboro; } #box { width: 100%; max-width: 400px; min-height: 400px; display: flex; flex-direction: column; justify-content: center; align-items: center; gap: 1rem; padding: 2rem; background: white; border-radius: 1rem; box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23); } #box form { display: flex; flex-direction: column; gap: 0.25rem; } .input-error { border-color: crimson; } .text-error { color: crimson; } </style> </head> <body> <div id="box"> <h2> Título del libro <h2/> </div> </body> </html>