http://jsbin.com/etozop/2/edit
put a div wrapper with WIDTH :
<p><fieldset style="width:60px;">
<div style="border:solid 1px red;width:80px;">
<input type="checkbox" id="a">
<label for="a">a</label>
<input type="checkbox" id="b">
<label for="b">b</label>
</div>
<input type="checkbox" id="c">
<label for="c">c</label>
</fieldset></p>
a name could be " john winston ono lennon" which is very long... so what do you want to do? (youll never know the length)... you could make a function that wraps after x chars like : "john winston o...."