CSS

borders for tables in html/css

/*For collapsed boarders*/
table, th, td {
  border: 1px solid black;
  border-collapse: collapse;
}

CSS Table Borders

table, th, td {
  border: 1px solid;
}

add border to table css

table, th, td {
    width: 20%;
    margin: auto;
    border: 1px solid black;
    border-collapse: collapse;

}