function changeVisibility(id)
{
    var obj = document.getElementById(id);
    
    if (obj.style.visibility == "visible") obj.style.visibility = "hidden";
    else obj.style.visibility = "visible";
    /*if (obj.style.display == "none") obj.style.display = "block";
    else obj.style.visibility = "none";*/
}

function Browser() {
    var ua, s, i;

    this.isIE = false;
    this.isNS = false;
    this.version = null;

    ua = navigator.userAgent;

    s = "MSIE";
    if ((i = ua.indexOf(s)) >= 0) {
        this.isIE = true;
        this.version = parseFloat(ua.substr(i + s.length));
        return;
    }

    s = "Netscape6/";
    if ((i = ua.indexOf(s)) >= 0) {
        this.isNS = true;
        this.version = parseFloat(ua.substr(i + s.length));
        return;
    }

    // Treat any other "Gecko" browser as NS 6.1.

    s = "Gecko";
    if ((i = ua.indexOf(s)) >= 0) {
        this.isNS = true;
        this.version = 6.1;
        return;
    }
}

var browser = new Browser();

// Global object to hold drag information.

var dragObj = new Object();
dragObj.zIndex = 0;

function dragStart(event, id) {

    var el;
    var x, y;
    
    // If an element id was given, find it. Otherwise use the element being
    // clicked on.

    if (id)
        dragObj.elNode = document.getElementById(id);
    else
    {
        if (browser.isIE)
            dragObj.elNode = window.event.srcElement;
        if (browser.isNS)
            dragObj.elNode = event.target;

        // If this is a text node, use its parent element.

        if (dragObj.elNode.nodeType == 3)
            dragObj.elNode = dragObj.elNode.parentNode;
    }

    // Get cursor position with respect to the page.

    if (browser.isIE) {
        x = window.event.clientX + document.documentElement.scrollLeft
        + document.body.scrollLeft;
        y = window.event.clientY + document.documentElement.scrollTop
        + document.body.scrollTop;
    }
    if (browser.isNS) {
        x = event.clientX + window.scrollX;
        y = event.clientY + window.scrollY;
    }

    if (dragObj.elNode.style.visibility == "hidden") return;
    
    // Save starting positions of cursor and element.

    dragObj.cursorStartX = x;
    dragObj.cursorStartY = y;
    dragObj.elStartLeft = parseInt(dragObj.elNode.style.left, 10);
    dragObj.elStartTop = parseInt(dragObj.elNode.style.top, 10);

    if (isNaN(dragObj.elStartLeft)) dragObj.elStartLeft = 0;
    if (isNaN(dragObj.elStartTop)) dragObj.elStartTop = 0;

    // Update element's z-index.

    //dragObj.elNode.style.zIndex = ++dragObj.zIndex;

    // Capture mousemove and mouseup events on the page.

    if (browser.isIE) {
        document.attachEvent("onmousemove", dragGo);
        document.attachEvent("onmouseup", dragStop);
        window.event.cancelBubble = true;
        window.event.returnValue = false;
    }
    if (browser.isNS) {
        document.addEventListener("mousemove", dragGo, true);
        document.addEventListener("mouseup", dragStop, true);
        event.preventDefault();
    }
}

function dragGo(event) {

    var x, y;

    // Get cursor position with respect to the page.

    if (browser.isIE) {
        x = window.event.clientX + document.documentElement.scrollLeft
        + document.body.scrollLeft;
        y = window.event.clientY + document.documentElement.scrollTop
        + document.body.scrollTop;
    }
    if (browser.isNS) {
        x = event.clientX + window.scrollX;
        y = event.clientY + window.scrollY;
    }

    // Move drag element by the same amount the cursor has moved.

    dragObj.elNode.style.left = (dragObj.elStartLeft + x - dragObj.cursorStartX) + "px";
    dragObj.elNode.style.top = (dragObj.elStartTop + y - dragObj.cursorStartY) + "px";

    if (browser.isIE) {
        window.event.cancelBubble = true;
        window.event.returnValue = false;
    }
    if (browser.isNS)
        event.preventDefault();
    }

function dragStop(event) {

    // Stop capturing mousemove and mouseup events.

    if (browser.isIE) {
        document.detachEvent("onmousemove", dragGo);
        document.detachEvent("onmouseup", dragStop);
    }
    if (browser.isNS) {
        document.removeEventListener("mousemove", dragGo, true);
        document.removeEventListener("mouseup", dragStop, true);
    }
}