Создание градиента
<style> .div { background-image: linear-gradient(#ff0000, #ffff00); width: 130px; height: 130px; border: 1px solid #aaa; } </style>
<style> .div { background-image: linear-gradient(#ff0000, #ffff00); width: 130px; height: 130px; border: 1px solid #aaa; } </style>