ExtJS (Javascript) 44
new Ext.Window({html:'Hello world',}).show()
Hello world window on jsfiddle
new Ext.Window({html:'Hello world',}).show()<link rel="stylesheet" type="text/css"
href="http://dev.sencha.com/deploy/dev/resources/css/ext-all.css"/>
<script type='text/javascript'
src="http://dev.sencha.com/deploy/dev/adapter/ext/ext-base.js"></script>
<script type='text/javascript'
src="http://dev.sencha.com/deploy/dev/ext-all.js"></script>