title: Upon selecting a value from a drop down list, another drop list will generate on the same page
body: <p>was wondering how can I create a sub drop down box upon selecting a value from the parent drop down box.</p>
  
  <p>Example : </p>
  
  <p>I ask the user to select "Which Page?" which in a form of a drop down box. The value are "About Us", "Products" and etc.</p>
  
  <p>If the user selects "Products", I want another drop down box with value example "MP3", "IPHONE" and etc to appear below the first drop down box on the same page.</p>
  
  <p>How can I do that? Advices please. Try searching on Google but not sure what to type in the search box.</p>