Como adicionar fronteira no CSS
.div1{
border: 10px;
border-color: #000000;
border-style: solid;
}
Shiv
.div1{
border: 10px;
border-color: #000000;
border-style: solid;
}/* style */
border: solid;
/* width | style */
border: 2px dotted;
/* style | color */
border: outset #f33;
/* width | style | color */
border: medium dashed green;
/* Global values */
border: inherit;
border: initial;
border: revert;
border: revert-layer;
border: unset;