$("textarea").keydown(function(e) {
var $this, end, start;
if (e.keyCode === 9) {
start = this.selectionStart;
end = this.selectionEnd;
$this = $(this);
$this.val($this.val().substring(0, start) + "\t" + $this.val().substring(end));
this.selectionStart = this.selectionEnd = start + 1;
return false;
}
});