<div id="textAreaDiv" style="visibility:hidden;"><textarea></textarea></div>

<input type="button" onClick="showTextArea()">
<input type="button" onClick="hideTextArea()">

<script>
function showTextArea() {
document.getElementById('textAreaDiv').style.visibility="visible";
}

function hideTextArea() {
document.getElementById('textAreaDiv').style.visibility="hidden";
}
</script>

or
To toggle the DIV with one button, you could do this:

<script>
function showHideTextarea() {
if (document.getElementById('textAreaDiv').style.visibility="hidden")
{
document.getElementById('textAreaDiv').style.visibility="visible";
}
else
{
document.getElementById('textAreaDiv').style.visibility="hidden";
}
}
</script>
And this doesn't need the JQuery library to use.

or

jaeart
http://flwebsites.biz/jAlert/