Reply To: Adding border bottom to widgets

on my end whenever i used #sidebar and .widget it didnt work

so

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

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

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

should all work