help me understand a variable setting
<pre><code>var fmt = document.documentElement.clientWidth;
        var cls = (fmt&lt;=240)?'pda_ver':(fmt&gt;240&amp;&amp;fmt&lt;=320)?'pda_hor':(fmt&gt;320&amp;&amp;fmt&lt;=640)?'screen_ultralow':(fmt&gt;640&amp;&amp;fmt&lt;=800)?'screen_low':(fmt&gt;800&amp;&amp;fmt&lt;=1024)?'screen_med':(fmt&gt;1024&amp;&amp;fmt&lt;=1280)?'screen_high':'screen_wide';
</code></pre>

<p>can someone tell me what this does (just the part where the variable is set with a value. I do not understand... what are the <code>?</code>, <code>:</code> have for a role here)? i have never seen a variable declared like that. Is this a conditional variable setting? if yes how does it work ?</p>

<p><a href="http://www.alistapart.com/d/switchymclayout/transition_layout_tab.html" rel="nofollow">working example</a></p>
