function test_why(box_id, dropdown){

//var info = document.getElementById(dropdown).value
var info = document.getElementById(dropdown);
var info1 = info[info.selectedIndex].value

if(info1 == 0){

var box = 'why_box_' + box_id
var drop = 'why_drop_' + box_id

document.getElementById(drop).display = 'none'
document.getElementById(box).display = 'block'

}

}


	<select name='why_dropdown_1' onchange='test_why(1, "why_dropdown_1")'>
	<option value='1'>DT. HBO mål</option>
	<option value='2'>DT. tider</option>
	<option value='3'>Vundet konkurrence</option>
	<option value='4'>Kasse tider</option>

	<option value='5'>Nået mål</option>
	<option value='0'>Skriv selv grund</option>
	</select>