̈ DIAERESIS UTF-8 character with hex code 0308

Using HEX code of DIAERESIS in HTML file

<span> &#x0308; </span>

Using Decimal code of DIAERESIS in HTML file

<span> &#776; </span>

Using HEX code of DIAERESIS in CSS file for content

span { 
    content: '\0308';
}