Procure por:
<script>
function click() {
if (event.button==2||event.button==3) {
oncontextmenu='return false';
}
}
document.onmousedown=click
document.oncontextmenu = new Function("return false;")
</script>
<script>
function click() {
if (event.button==2||event.button==3) {
oncontextmenu='return false';
}
}
document.onmousedown=click
document.oncontextmenu = new Function("return false;")
</script>