function clickIE() 
{
    if (document.all)
    {
        return false;
    }
}

function clickNS(e) 
{
    if(document.layers || (document.getElementById && !document.all))
    {
        if(e.which==2 || e.which==3) 
        {
            return false;
        }
    }
}

if (document.layers)
{
    document.captureEvents(Event.MOUSEDOWN);
    document.onmousedown=clickNS;
}
else
{
    document.onmouseup=clickNS;
    document.oncontextmenu=clickIE;
}

document.oncontextmenu = new Function('return false');