aa.js

// This assumes you're using jQuery. This does the heavy lifting.
function setPlaceholderText() {
	var PLACEHOLDER_SUPPORTED = 'placeholder' in document.createElement('input');
	if (PLACEHOLDER_SUPPORTED || !$(':input[placeholder]').length) {
		return;
	}

	$(':input[placeholder]').each(function() {
		var el = $(this);
		var text = el.attr('placeholder');

		function add_placeholder() {
			if (!el.val() || el.val() === text) {
				el.val(text).addClass('placeholder_text');
			}
		}

		add_placeholder();

		el.focus(function() {
			if (el.val() === text) {
				el.val('').removeClass('placeholder_text');;
			}
		}).blur(function() {
			if (!el.val()) {
				el.val(text).addClass('placeholder_text');;
			}
		});

		el.closest('form').submit(function() {
			if (el.val() === text) {
				el.val('');
			}
		}).bind('reset', function() {
			setTimeout(add_placeholder, 50);
		});
	});
}