<input type="button" onclick="some_button_click(ann)" value="Объявление" />

<script type="text/javascript">
function setcookie(a,b,c) {if(c){var d = new Date();d.setDate(d.getDate()+c);}if(a && b) document.cookie = a+'='+b+(c ? '; expires='+d.toUTCString() : '');else return false;}
function getcookie(a) {var b = new RegExp(a+'=([^;]){1,}');var c = b.exec(document.cookie);if(c) c = c[0].split('=');else return false;return c[1] ? c[1] : false;}
function rmcookie(a) {var d = new Date();d.setDate(d.getDate()-900);if(a) document.cookie = a+'=a; expires='+d.toUTCString();else return false;}
var ann = document.getElementById("pun-announcement");
function hide_ann(ann){setcookie('announce','hide'); ann.style.display='none';}
function show_ann(ann){setcookie('announce','show'); ann.style.display='block';}
function some_button_click(ann){if(getcookie('announce')=='hide') show_ann(ann); else hide_ann(ann)}
if(getcookie('announce')=='hide') hide_ann(ann); else show_ann(ann);
</script>