HOW TO PERFORM AN ACTION AN OPTION IS CLICKED IN DROP DOWN
<select id="dropdown" onChange="showHide()">
<option value="A">option1</option>
<option value="B">option2</option>
<option value="C">option3</option>
<option value="D">option4</option>
</select>
function showHide()
{
hideAll();
var val = document.getElementById("dropdown").value;
if(val == "A")
document.getElementById("firstTextBoxId").style.display = 'block';
else if(val == "B")
document.getElementById("secondTextBoxId").style.display = 'block';
else if(val == "C")
document.getElementById("ThirdTextBoxId").style.display = 'block';
else if(val == "D")
document.getElementById("FourthTextBoxId").style.display = 'block';
}
function hideAll()
{
document.getElementById("firstTextBoxId").style.display = 'none';
document.getElementById("secondTextBoxId").style.display = 'none';
document.getElementById("thirdTextBoxId").style.display = 'none';
document.getElementById("fourthTextBoxId").style.display = 'none';
}