The width of the dialog.
Examples
Fixed Width
<div id="dialog">Lorem ipsum dolor sit amet, consectetur adipiscing elit...</div>
<script>
$("#dialog").dialog({
width: 400
});
</script>
Auto Width
<div id="dialog" title="Wikipedia">
<img src="https://upload.wikimedia.org/wikipedia/en/thumb/8/80/Wikipedia-logo-v2.svg/1122px-Wikipedia-logo-v2.svg.png" width="420"/>
</div>
<script>
$("#dialog").dialog({
width: 'auto'
});
</script>