С CAPITAL LETTER ES UTF-8 character with hex code 0421

Using HEX code of CAPITAL LETTER ES in HTML file

<span> &#x0421; </span>

Using Decimal code of CAPITAL LETTER ES in HTML file

<span> &#1057; </span>

Using HEX code of CAPITAL LETTER ES in CSS file for content

span { 
    content: '\0421';
}