How To Set Username Font size in postbit

[shzad1]

yes
here it is the content

/* ***** styling for 'big' usernames on postbit etc. ***** */
.bigusername { font-size: 14pt; }

/* ***** small padding on 'thead' elements ***** */
td.thead, th.thead, div.thead { padding: 4px; }

/* ***** basic styles for multi-page nav elements */
.pagenav a { text-decoration: none; }
.pagenav td { padding: 2px 4px 2px 4px; }

/* ***** de-emphasized text */
.shade, a.shade:link, a.shade:visited { color: #777777; text-decoration: none; }
a.shade:active, a.shade:hover { color: #FF4400; text-decoration: underline; }
.tcat .shade, .thead .shade, .tfoot .shade { color: #DDDDDD; }

/* ***** define margin and font-size for elements inside panels ***** */
.fieldset { margin-bottom: 6px; }
.fieldset, .fieldset td, .fieldset p, .fieldset li { font-size: 11px; }

what to do the postbit size apply for all usergroups?
really needs help