How to Create Boxes with Rounded Corners in CSS | Webucator
border-radius – Lea Verou
Keeping inside the rounded corners with CSS
html - How can I add outer rounded corners to a div? - Stack Overflow
border-top-left-radius - CSS | MDN
How to add rounded corner to an element using CSS ? - GeeksforGeeks
html - How to make div with round corner totally opaque inside, but colored outside (between round border line and original border-box line)? - Stack Overflow
CSS Border Radius | A Quick Glance of CSS Border Radius | Examples