SOURCE

<p>loream lajkd;fja;ldfkla;sjkfd;laskdf;laksdfl;asd;lfkajsljf;a</p>
<p class="error-line">loream lajkd;fja;ldfkla;sjkfd;laskdf;laksdfl;asd;lfkajsljf;a</p>
<p>loream lajkd;fja;ldfkla;sjkfd;laskdf;laksdfl;asd;lfkajsljf;a</p>
<p class="base-line">loream lajkd;fja;ldfkla;sjkfd;laskdf;laksdfl;asd;lfkajsljf;a</p>

    .error-line {
        position: relative;
        font-size: 14x;
        --color: red;
    }

    .error-line::after {
        content: "";
        position: absolute;
        left: 0;
        bottom: -0.825em;
        width: 100%;
        height: 1em;
        background: linear-gradient(135deg, transparent, transparent 45%, var(--color), transparent 55%, transparent 100%), linear-gradient(45deg, transparent, transparent 45%, var(--color), transparent 55%, transparent 100%);
        background-size: 0.8em 0.8em;
        background-repeat: repeat-x, repeat-x;
    }

    .base-line {
        position: relative;

    }

    .base-line::after {
        content: "";
        position: absolute;
        left: 0;
        bottom: -0.3em;
        width: 100%;
        height: 0.3em;
        background: linear-gradient(45deg, transparent, transparent 45%, red, transparent 55%), linear-gradient(135deg, transparent, transparent 45%, red, transparent 55%);
        background-size: 0.6em 0.6em;
        background-repeat: repeat-x;
    }