function derecha(e) {
if (navigator.appName == 'Netscape' && (e.which == 3 || e.which == 2)){
alert('Copyright Gruas SegoviaŽ 2006-2007')
return false;
}

else if (navigator.appName == 'Microsoft Internet Explorer' && (event.button == 2)){
alert('Copyright Gruas SegoviaŽ 2006-2007')
}
}
document.onmousedown=derecha