CodePen

HTML

            
              <form>
    <select name="qwer" onChange="changeText(this.form);">
        <option value="0">Select</option>
        <option value="1">One</option>
        <option value="2">Two</option>
    </select>
    <br>
    <div id="display">Select from the list to change this box</div> 
</form>
            
          
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CSS

            
              
            
          
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JS

            
              var textBlocks = new Array(
        'Select from the list to change this box',
        'Text block two',
        'Text block three'
); 

function changeText(form) {
    var ind = form.qwer.selectedIndex;
    document.getElementById("display").innerHTML=textBlocks[ind]; 
}
            
          
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