gistfile1.js

dynamicLabel = function($input, $label) {

		// exit if either element isn't found
		if ( !($input[0] && $label[0]) ) { return; }

		function hideLabel() {
			$label.hide();
		}

		function showLabelIfInputEmpty() {
			!$input.val() && $label.show();
		}

		$input.keydown(hideLabel).focus(hideLabel).blur(showLabelIfInputEmpty);
		showLabelIfInputEmpty();
	}
}



var $inputelement = $('#yourinputelement'),
dynamicLabel( $inputelement, $inputelement.prev() );