NS4 = (document.layers) ? 1 : 0;
IE4 = (document.all) ? 1 : 0;
ver4 = (NS4 || IE4) ? 1 : 0;

if (ver4) {			//定义各个层的位置及显示状态
    with (document) {
        write("<STYLE TYPE='text/css'>");
        if (NS4) {
            write(".parent {position:absolute; visibility:visible}");
            write(".child {position:absolute; visibility:visible}");
            write(".regular {position:absolute; visibility:visible}")
        }
        else {
            write(".child {display:none}")
        }
        write("</STYLE>");
    }
}

function getIndex(el) {			//获得变量ind的值
    ind = null;
    for (i=0; i<document.layers.length; i++) {
        whichEl = document.layers[i];
        if (whichEl.id == el) {
            ind = i;
            break;
        }
    }
    return ind;
}

function arrange() {		//定义一下页面上元素的位置。当菜单打开时，页面上菜单以下的东西的位置顺序往下推，菜单合起时，菜单以下的东西自动上移
    nextY = document.layers[firstInd].pageY +document.layers[firstInd].document.height;
    for (i=firstInd+1; i<document.layers.length; i++) {
        whichEl = document.layers[i];
        if (whichEl.visibility != "hide") {
            whichEl.pageY = nextY;
            nextY += whichEl.document.height;
        }
    }
}

function initIt(){			//初始化菜单，让页面载入时，菜单处于未打开状态
    if (!ver4) return;
    if (NS4) {
        for (i=0; i<document.layers.length; i++) {
            whichEl = document.layers[i];
            if (whichEl.id.indexOf("Child") != -1) whichEl.visibility = "hide";
       }
        arrange();
    }
    else {
        divColl = document.all.tags("DIV");
        for (i=0; i<divColl.length; i++) {
            whichEl = divColl(i);
            if (whichEl.className == "child") whichEl.style.display = "none";
        }
    }
}

function expandIt(el) {			//由于层的可见状态在IE浏览器和NetScape浏览器中的解释是不同的，所以要分别讨论，判断菜单的状态。如果菜单是打开的，那么当再点击时，子菜单就不可见；如果菜单是关闭状态，那么当再点击时，子菜单就可见
   	initIt();
    if (!ver4) return;
    if (IE4) {
        whichEl = eval(el + "Child");
        if (whichEl.style.display == "none") {
            whichEl.style.display = "block";
        }
        else {
            whichEl.style.display = "none";
        }
    }
    else {
        whichEl = eval("document." + el + "Child");
        if (whichEl.visibility == "hide") {
            whichEl.visibility = "show";
        }
        else {
            whichEl.visibility = "hide";
        }
        arrange();
    }
}
onload = initIt;


if (NS4) {		//如果用户的浏览器是NetScape，先初始化一下变量
        firstEl = "KB1Parent";
        firstInd = getIndex(firstEl);
        arrange();
}