i would like to show a drop down box or an input textbox based on user selection. for example, i have a drop down box in the first place, in which i have 4 options, such as a, b, c and d inside. if user chose a or b, i want to show the textbox and if the user chose c or d, the dropdownbox will be shown. how do initiate these dropdownbox and textbox in the client side????