Most web browsers these days do not explicitly handle html text styling - SUB, SUP, B, I and so on - they (kinda sorta) are converted into SPAN elements with appropriate CSS properties, and the rendering engine only deals with that.

style-fixture.css

/*
*      Most web browsers these days do not explicitly handle
*      html text styling - SUB, SUP, B, I and so on - they (kinda
*      sorta) are converted into SPAN elements with appropriate CSS
*      properties, and the rendering engine only deals with that.
*      
*/

/*  B for bold */
.bold {
  font-weight: bold;
}

/* I for italic */
.italic {
font-style: italic;
}

/* SUP -> superscript */ 
.superscript {
    font-size: .83em;
    line-height: 0.5em;
    vertical-align: baseline;
    position: relative;
    top: -0.4em;
}