.dashed-gradient{
height: 100px;
width: 200px;
padding: 10px;
background-image: linear-gradient(to right, blue 50%, transparent 50%), linear-gradient(to right, blue 50%, transparent 50%), linear-gradient(to bottom, blue 50%, transparent 50%), linear-gradient(to bottom, blue 50%, transparent 50%);
background-position: left top, left bottom, left top, right top;
background-repeat: repeat-x, repeat-x, repeat-y, repeat-y;
background-size: 20px 3px, 20px 3px, 3px 20px, 3px 20px;
}
.dashed-repeating-gradient {
height: 100px;
width: 200px;
padding: 10px;
background-image: repeating-linear-gradient(to right, blue 0%, blue 50%, transparent 50%, transparent 100%), repeating-linear-gradient(to right, blue 0%, blue 50%, transparent 50%, transparent 100%), repeating-linear-gradient(to bottom, blue 0%, blue 50%, transparent 50%, transparent 100%), repeating-linear-gradient(to bottom, blue 0%, blue 50%, transparent 50%, transparent 100%);
background-position: left top, left bottom, left top, right top;
background-repeat: repeat-x, repeat-x, repeat-y, repeat-y;
background-size: 20px 3px, 20px 3px, 3px 20px, 3px 20px;
}
/* just for demo */
div {
margin: 10px;
transition: all 1s;
}
div:hover {
height: 150px;
width: 300px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<div class='dashed-gradient'>Some content</div>
<div class='dashed-repeating-gradient'>Some content</div>
border-style: solid
(ou quelque chose de similaire) si vous omettez le remplacement.