How to adjust the width of a HTML combobox (Drop down box or Select box)

<select style="width:200px;">
    <option>Option 1</option>
    <option>Option 2</option>
    <option>Option 3</option>
</select>

HTML

<select class="dropdown">
    <option>Option 1</option>
    <option>Option 2</option>
    <option>Option 3</option>
</select>

CSS

.dropdown{
    width: 200px;
}