Positioning Javascript

I have a button that when clicked adds a select box. How can i get it to position directly underneath the button.

javascript:

function add_course(){

var course0=document.createElement('option');
course0.value='ASP';
course0.innerHTML='ASP';

var Course=document.createElement('select');

Course.name='Course';
Course.appendChild(course0);

document.forms.Registration.appendChild(Course);

}


html code:

<input name="add_courses" type="button" class="submit" onClick="add_course()" value="Add More Courses">