CSS - Hide elements (class) based on value of select box

Answer 1

This can't be done using a <select> item, however because of the pseudo class :checked states of checkboxes and radio buttons, you can accomplish what you wanted using those instead:

HTML

<input type="radio" id="supportCase" name="radios"> 
<label for="supportCase">Support Case</label>
<input type="radio" id="other" name="radios"> 
<label for="other">Other</label>
    <br />
<label class="applicableSupportCase">Device:</label>

CSS

input[id=other]:checked ~ .applicableSupportCase {
  visibility:hidden;
}

I used visibility, but you can change the attribute to whatever you want.

If you want an ease in and out, then create the same statement using the :not(:checked) pseudo class:

input[id=other]:not(:checked) ~ .applicableSupportCase {
  //whatever ease(out) you want here
}

JSFiddle: http://jsfiddle.net/ja2ud1Lf/