IE4plus = (document.all) ? true : false;
NS4 = (document.layers) ? true : false;

function clickIE()

{
return false;
}

function clickNS(e)

{
if (e.which==2 || e.which==3)

{
return false;
}

}
if (!IE4plus)

{
document.captureEvents(Event.MOUSEDOWN || Event.MOUSEUP);
document.onmousedown=clickNS;
document.onmouseup= clickNS;
document.oncontextmenu=clickIE;
}

else 

{
document.onmouseup= clickIE;
document.oncontextmenu=clickIE;
}