jquery.pre_Input.js

(function($) {

$.fn.preInput = function(txt, options) {
	var default_options = {
		class_name: 'pre-input'
	};

	options = $.merge(default_options, options || {});
	return this.each(function(){
		if(typeof this.value == 'undefined') return;

		var elm = $(this);
		elm.val(txt)
		elm.addClass(options.class_name)
		elm.focus(function(){
			if(elm.val() == txt) {
				elm.removeClass(options.class_name)
				elm.val('');
			}
		});
		elm.blur(function(){
			if(elm.val() == '') {
				elm.addClass(options.class_name)
				elm.val(txt)
			}
		});
	});
}

})(jQuery);