css - Header cant have a border

Question

border-width doesn't work.

header {
    background-color: #58ACFA;
    text-align: center;
    border-width: 5px;
    border-color: black;
}

I tried to use border-size and it did not work.

How can I do it?

Answer 1

header {
    background-color: #58ACFA;
    text-align: center;
    border-style: solid;
    border-width: 5px;
    border-color: black;
}

你概率。忘记边框样式。我给你加了。也可以一行完成

border: 5px solid #000;

Answer 2

尝试：

header {
    background-color: #58ACFA;
    text-align: center;
    border: 5px solid black;
}

这与

header {
    background-color: #58ACFA;
    text-align: center;
    border-style: solid;
    border-width: 5px;
    border-color: black;
}