<script language='JavaScript'>
function hw() {
if(document.getElementById('jjj').style.display == "none") {
document.getElementById('jjj').style.display = "block";
document.getElementById('btn').value = "-";
}
else {
document.getElementById('jjj').style.display = "none";
document.getElementById('btn').value = "+";
}
}
</script>
<input type='button' onclick='hw();' id='btn' value='-'><br>
<div id='jjj' style='background-color:Silver;width:200px;height:200px;'></div>