box-sizing: content-box;
border-width: 8px;
border-style: solid;
border-image: linear-gradient(to right bottom, #260B3C, #a053df);
border-image-slice: 1;.rounded-corners-gradient-borders {
width: 300px;
height: 80px;
border: double 4px transparent;
border-radius: 80px;
background-image: linear-gradient(white, white), radial-gradient(circle at top left, #f00,#3020ff);
background-origin: border-box;
background-clip: content-box, border-box;
}
div{
width: 300px;
height: 80px;
border: double 5px transparent;
border-radius: 30px;
background-image: linear-gradient(white, white), /*here must be*/
linear-gradient(to right, green, gold); /*both gradients*/
background-origin: border-box;
background-clip: content-box, border-box;
}