[Javascript] dynamically changing CSS in NN4.7

[Lau]

I want to dynamically change the CLASS of a link when its clicked, I got it working in IE but of
course NN4.7 is giving me grief again.
can anyone help?

<A HREF='#' CLASS=LkTopLx onclick='ChangeClass(this);'>hello</A>

function ChangeClass(p_this){
p_this.className="LkOptSel"
}