javascript get user selected text

IE version:
document.selection.createRange().duplicate().text;

Firefox version:
document.getSelection();

For all browser selected():
<input type="button" onclick="alert(selected())" />
<script type="text/javascript">
    function selected(){
        if (document.selection) return document.selection.createRange().duplicate().text;
        else return document.getSelection();
    }
</script>