<script>
function DoCheckUncheckDisplay(d,dchecked,dunchecked)
{
   if( d.checked == true )
   {
      document.getElementById(dchecked).style.display = "block";
      document.getElementById(dunchecked).style.display = "none";
   }
   else
   {
      document.getElementById(dchecked).style.display = "none";
      document.getElementById(dunchecked).style.display = "block";
   }
}
</script>

<div>
Check/uncheck: 
<input type="checkbox" onclick="DoCheckUncheckDisplay(this,'checkbox-checked')" style="margin:0;">
</div>

<div id="checkbox-checked" style="display:none; color:green;">
The checkbox is checked.
</div>

<div>
Check/uncheck: 
<input type="checkbox" onclick="DoCheckUncheckDisplay(this,'checkbox-checked1')" style="margin:0;">
</div>

<div id="checkbox-checked1" style="display:none; color:green;">
The checkbox1 is checked.
</div>