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<script>
var stateObj = { foo: 'bar' };
history.pushState(stateObj, 'page 2', 'sistema');
</script>

<SCRIPT type="text/javascript">
window.history.forward();
function noBack() { window.history.forward(); }
</SCRIPT>

<BODY onload="noBack();"
onpageshow="if (event.persisted) noBack();" onunload="">
</body>

pref browser.sessionhistory.max_entries to 0