[@robkk Moderator 12 years, 3 months ago]

#bbp_topics_widget-4 ul li {
border-bottom: 1px solid #F1F1F1;
}

they work on my end

do

#bbp_topics_widget-4 ul li {
border-bottom: 1px solid #F1F1F1!important;
}

or clear your cache