function adjustLayout()
{
    var navObj = new getObj('navBar');
    var mainObj = new getObj('mainContent');

    var navHeight = parseInt(navObj.obj.offsetHeight);
    var mainHeight = parseInt(mainObj.obj.offsetHeight);

    if(navHeight < mainHeight)
    {
       navObj.style.height = mainHeight - 2 + 'px';
    }

    if(navHeight > mainHeight)
    {
       mainObj.style.height = navHeight + 'px';
    }

    if(parseInt(navObj.obj.offsetHeight) < 420)
    {
       mainObj.style.height = '420px';
       navObj.style.height = '420px';
    }
}

function getObj(name)
{
    if (document.getElementById)
    { this.obj = document.getElementById(name); this.style = document.getElementById(name).style; }
    else if (document.all)
    { this.obj = document.all[name]; this.style = document.all[name].style; }
    else if (document.layers)
    { this.obj = document.layers[name]; this.style = this.obj; }
}

window.onresize = adjustLayout;