How to edit the border-radius on the forums!?

[InVaLiD]

.thread_legend,
.thread_legend dd {
margin: 0;
padding: 0;
}

.thread_legend dd {
padding-bottom: 4px;
margin-right: 15px;
}

.thread_legend img {
margin-right: 4px;
vertical-align: bottom;
}

That's all I have for .thread in global.css.