HTML Code:
<div id="welcomeDiv" style="display:none;" class="answer_list" > WELCOME</div>
<input type="button" name="answer" value="Show Div" onclick="showDiv()" />
Javascript:
function showDiv() {
document.getElementById('welcomeDiv').style.display = "block";
}
See the Demo: http://jsfiddle.net/rathoreahsan/vzmnJ/