var timeout    = 500;
var closetimer    = 0;
var ddmenuitem    = 0;
var ddmenuanchor  = 0;

// open hidden layer
function mopen(id)
{    
    // cancel close timer
    mcancelclosetime();

    // close old layer
    mclose();

    // get new layer and show it
    ddmenuitem = document.getElementById(id);
    ddmenuitem.style.visibility = 'visible';
    ddmenuanchor = document.getElementById('a' + id);
    ddmenuanchor.style.background = 'url("Html/Images/menu_highlight.gif") repeat-x';
}
// close showed layer
function mclose()
{
    if(ddmenuitem)
    {
        ddmenuitem.style.visibility = 'hidden';
        ddmenuanchor.style.background = '#fff';
    }
}

// go close timer
function mclosetime()
{
    closetimer = window.setTimeout(mclose, timeout);
}

// cancel close timer
function mcancelclosetime()
{
    if(closetimer)
    {
        window.clearTimeout(closetimer);
        closetimer = null;
    }
}

// close layer when click-out
document.onclick = mclose;