How to make select elements shrink to max-width percent style within fieldset

The problem

This isn’t possible, at least if you only use max-width (see below for solution). <select>s are always a little bit tricky to style, as they’re interactive content elements and form control elements. As such, they have to follow some implicit rules. For one, you cannot make a select less wide than one of its options when using max-width. Think of the following scenario:

+------------------------------------+-+
|Another entry                       |v|
+------------------------------------+-+
|Another entry                         |
|Select box, select anything, please   |
|Another entry                         |
|Another entry                         |
+------------------------------------+-+

Let’s say that you want to squeeze this <select> – what will happen? The select’s width will get lesser, until…

+------------------------------------+-+   +-----------------------------------+-+
|Another entry                       |v|   |Another entry                      |v|
+------------------------------------+-+   +-----------------------------------+-+
|Another entry                         |   |Another entry                        | 
|Select box, select anything, please   |-->|Select box, select anything, please  | 
|Another entry                         |   |Another entry                        | 
|Another entry                         |   |Another entry                        | 
+------------------------------------+-+   +-----------------------------------+-+ 
                                                   |
           +---------------------------------------+
           v
+----------------------------------+-+   +---------------------------------+-+
|Another entry                     |v|   |Another entry                    |v|
+----------------------------------+-+   +---------------------------------+-+
|Another entry                       |   |Another entry                      | 
|Select box, select anything, please |-->|Select box, select anything, please| 
|Another entry                       |   |Another entry                      | 
|Another entry                       |   |Another entry                      | 
+----------------------------------+-+   +---------------------------------+-+ 

And then the process will stop, as the <option>s wouldn’t fit anymore. Keep in mind that you can’t style <option>s or at least only a little bit (color, font-variant) without getting some nasty quirks. However, the border-box can be changed, if the select is prepared correctly:

The solution

Use a width value on the select. Yep, it’s easy as that:

<fieldset style="background:blue;">
 <select name=countries style="width:100%;max-width:90%;">
  <option value=gs>South Georgia and the South Sandwich Islands</option>
 </select>
</fieldset>

Why does this work? Because the option will now recognize the width of the select correctly and won’t force the select to have a implicit min-width. Notice that the width is absurd, as it is more than the max-width. Most browsers won’t care and use the max-width in this case, as it provides an upper bound.

JSFiddle Demo (works in FF12, Chrome 18, IE9, Opera 11.60)

Edit

Wrapper based solution, this won’t change the original width:

<fieldset style="background:blue;">
<div style="display:inline-block;max-width:90%;"> <!-- additional wrapper -->
 <select name=countries style="width:100%">
  <option value=gs>South Georgia and the South Sandwich Islands</option>
 </select>
</div>
</fieldset>

JSFiddle Demo (works in browsers listed above)