Grab http://blog.kissmetrics.com/common/images/required.png as example for a required image .

NOTE: You probably don't want to use this trcik, but rather go for the defacto standard of a red asterisk to mark something required. An asterisk is language-independant and recognisable.

#content .post_comment p input.required {layout.c...228110886 (regel (409)
background:#FFFFFF url(../images/required.png) no-repeat scroll 254px 6px;
padding-right:63px;
width:242px;
}