isIE=document.all;
isNN=!document.all&&document.getElementById;
isN4=document.layers;

if (isIE||isNN){
document.oncontextmenu=checkclick;
}else{
document.captureEvents(Event.MOUSEDOWN || Event.MOUSEUP);
document.onmousedown=checkclick;}

function checkclick(e){
if (isN4){
if (e.which==2||e.which==3){
alert("Sorry for the inconvenience, this website does not permit the use of right-click contextual menus.");
return false;
}}else{
alert("Sorry for the inconvenience, this website does not permit the use of right-click contextual menus.");
return false;}}