这种效果如何做？

<style type="text/css">
.qiu1{
color:blue;
background:#339900;
font-weight:700;
font-style:normal;
}
.qiu2{
color:red;
background:#FFCC33;
font-weight:600;
font-style:italic;
}
</style>
</HEAD><BODY onload="go();">
<INPUT TYPE="button" id="b1" NAME="b1" value="Button1" class="qiu1" onclick="this.className=='qiu1'?this.className='qiu2':this.className='qiu1';">
<INPUT TYPE="button" id="b2" NAME="b2" value="Button2" class="qiu2" onclick="this.className=='qiu1'?this.className='qiu2':this.className='qiu1';">
<INPUT TYPE="button" id="b3" NAME="b3" value="Button3" class="qiu1" onclick="this.className=='qiu1'?this.className='qiu2':this.className='qiu1';">
</BODY>
</HTML>