下拉菜单

                <div id="LM1" class="lefdfl"> 
                    <div id="treePicb1" class="png lmenud" onclick="javascript:ShowFLTb(1)">主菜单</div>
                    <div id="LMb1" style="display:none"  class="pclist"><ul>
                        <li><a href="#">下拉列表</a></li>
                        <li><a href="#">下拉列表</a></li>
                    </ul></div>
                </div>



var number = 20;
function LMYC(obj) {
    var lbmc
    var treePic
    for (i = 1; i <= number; i++) {
        lbmc = document.getElementById('LM' + i);
        if (lbmcb != null) {
            treePic = document.getElementById('treePic' + i);
            treePic.className = 'lmenub';
            lbmc.style.display = 'none';
        }
    }
}
function ShowFLT(i) {
    lbmc = document.getElementById('LM' + i);
    treePic = document.getElementById('treePic' + i)
    if (lbmc.style.display == 'none') {
        LMYC();
        treePic.className = 'lmenua';
        lbmc.style.display = '';