Creates a close button X in pure CSS

another-close-x-pure-css.html

<span class="close-x"></span>
<style>
    .close-x {
        display: inline-block;
        width: 20px;
        height: 20px;
        border: 7px solid #f56b00;
        background:
            linear-gradient(45deg, rgba(0,0,0,0) 0%,rgba(0,0,0,0) 43%,#fff 45%,#fff 55%,rgba(0,0,0,0) 57%,rgba(0,0,0,0) 100%),
            linear-gradient(135deg, #f56b00 0%,#f56b00 43%,#fff 45%,#fff 55%,#f56b00 57%,#f56b00 100%);
    }
</style>